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Baba AI, Câtoi C. Comparative Oncology. Bucharest (RO): The Publishing House of the Romanian Academy; 2007.

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Comparative Oncology.

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Urinary tract tumors are less frequent, with the mention that in cattle, urinary bladder tumors in enzootic hematuria syndrome have a high incidence. The examination of kidneys in the slaughter house reveals in 1 million animals, a tumor incidence of 8.5 cases in cattle, 0.9 cases in sheep and 4.3 cases in swine [26]. Renal tumors are estimated at approximately 0.15% in horses, 1% in dogs, and 0.5% in felines [17].

Urinary bladder tumors are estimated at approximately 0.5% in dogs as well as in cattle. In dogs, similarly to humans, the male sex has a higher incidence of urinary tract tumors compared to females. The more frequently affected dog breeds are: Scottish Terrier, Shetland Sheepdog, Beagle and Collie. Advanced age in animals is a risk factor.

Risk factors for urinary tract neoplasms are industrial chemical substances (2-naphthylamine, benzidine), tryptophan metabolites (ortho-aminophenol), chronic irritations, viruses, fern and cyclophosphamide.

Histological Classification of Tumors of the Urinary System of Domestic Animals (Meuten et al. 2004)

Renal Tumors

  1. Epithelial Tumors
    • 1.1 Adenoma
    • 1.2 Carcinoma
      • 1.1.1 Renal adenocarcinoma
      • 1.1.2 Transitional cell carcinoma
      • 1.1.3 Squamous cell carcinoma
      • 1.1.4 Undifferentiated carcinoma
    • 1.3 Oncocytoma
  2. Embryonal Tumors
    • 2.1 Nephroblastoma (embryonal nephroma)
    • 2.2 Thoracolumbar spinal cord tumor of young dogs (nephroblastoma)
  3. Mesenchymal Tumors
    • 3.1 Tumors of vascular tissue
      • 3.1.1 Hemangioma
      • 3.1.2 Hemangiosarcoma
    • 3.2 Tumors of fibrous tissue
      • 3.2.1 Fibroma
      • 3.2.2 Renal interstitial cell tumor
  4. Metastatic Tumors
    • 4.1 Lymphoma
    • 4.2 Hemangiosarcoma
    • 4.3 Carcinoma
  5. Tumorlike Lesions
    • 5.1 Malformations
      • 5.1.1 Hamartoma
      • 5.1.2 Telangiectasia
    • 5.2 Granulomas
    • 5.3 Cysts
      • 5.3.1 Solitary cyst
      • 5.3.2 Multiple cysts (polycystic kidney)

Renal Pelvis and Ureteral Tumors

  1. Epithelial Tumors
    • 1.1 Transitional cell carcinoma
    • 1.2 Papilloma
  2. Mesenchymal Tumors
    • 2.1 Hemangioma

Urinary Bladder Tumors

  1. Epithelial Tumors
    • 1.1 Papilloma
    • 1.2 Adenoma
    • 1.3 Carcinoma
      • 1.3.1 Transitional cell carcinoma
        • Papillary and infiltrating
        • Papillary and noninfiltrating
        • Nonpapillary and infiltrating
        • Nonpapillary and noninfiltrating (carcinoma in situ)
      • 1.3.2 Squamous cell carcinoma
      • 1.3.3 Adenocarcinoma
      • 1.3.4 Undijferentiated carcinoma
  2. Mesenchymal Tumors
    • 2.1 Tumors of skeletal muscle
      • 2.1.1 Rhabdomyosarcoma
        • Botryoid rhabdomyosarcoma
    • 2.2 Tumors of smooth muscle
      • 2.2.1 Leiomyoma
      • 2.2.2 Leiomyosarcoma
    • 2.3 Tumors of vascular tissue
      • 2.3.1 Hemangioma
      • 2.3.2 Hemangiosarcoma
    • 2.4 Tumors of fibrous tissue
      • 2.4.1 Fibroma
      • 2.4.2 Fibrosarcoma
  3. Secondary Tumors
    • 3.1 Lymphoma
  4. Tumorlike Lesions
    • 4.1 Polypoid cystitis
      • 4.1.1 Polypoid eosinophilic cystitis
    • 4.2 Polyp
    • 4.3 Metaplasia
      • 4.3.1 Glandular metaplasia (cystitis glandularis)
      • 4.3.2 Squamous metaplasia
    • 4.4 Brunn’s nests

Urethral Tumors

  1. Epithelial Tumors
    • 1.1 Squamous cell carcinoma
    • 1.2 Transitional cell carcinoma


The most frequently diagnosed renal neoplasms are carcinomas and nephroblastomas. Renal carcinomas have a higher incidence in dogs and cattle, while nephroblastomas are more frequent in swine, dogs and calves. In dogs, renal carcinomas are located in the papillary segment of the kidney, with the remark of a vascular invasion in the posterior vena cava and pulmonary metastasis [20].

The classification of renal tumors, more extensive according to NIELSEN et al. (1976), more pragmatic according to MAXIE and PRESCOTT (1993), can be synthesized as follows:

  1. epithelial tumors of the renal parenchyma: adenoma; carcinoma;
  2. epithelial tumors of the renal pelvis: papilloma; carcinoma; squamous cell carcinoma.
  3. undifferentiated carcinoma;
  4. nephroblastoma;
  5. mesenchymal tumors;
  6. malignant lymphoma (lymphosarcoma);
  7. teratoma;
  8. secondary tumors;
  9. unclassified tumors;
  10. tumor-like lesions; white renal spots in calves; granulomas in feline infectious peritonitis; hamartoma and cysts.

The study of 54 primary renal tumors in dogs, performed by KLEIN et al. (1988), revealed that 85.2% of these were epithelial neoplasms, 11.1% mesenchymal neoplasms, and 3.7% mixed neoplasms. The majority of tumors were malignant, and middle and old age groups were the most affected. Epithelial origin tumors had a clear predominance in males. Radiographically, 48% of cases presented lung metastases. Two German Shepherd dogs, diagnosed with multiple renal cystadenocarcinomas, also presented nodular dermatofibrosis.

Familial renal tumors have been reported in rats and German Shepherd dogs. The Eker rat is a model for hereditary renal carcinoma in which a single tumor suppressor gene, the Tsc-2 gene on chromosome 10ql2, has been identified and is responsible for cancer induction. Heterozygote animals develop bilateral, multicentric renal cell tumors (adenomas/carcinomas) at an early age. The cancer trait is inherited as an autosomal dominant condition, being embryolethal in the homozygous state. In laboratory animal models to date, neither ras family oncogenes nor the p53 tumor suppressor has been commonly altered in renal neoplasia, although ras mutations have been noted in some rat nephroblastomas and chemically induced renal cell tumors [39].

13.1.1. Adenoma

Adenoma is a benign tumor of the tubular epithelium, which is rarely found, as a necropsy surprise, being reported in cattle and horses, exceptionally in cats [4]. Statistics have not established a predisposition depending on age, breed or sex.

Macroscopically, adenoma appears as a small, well circumscribed formation, around 2 cm in diameter, of white-gray or yellowish color, located in the renal cortex. Necrotic and/or hemorrhagic foci can be found in section.

Histologically, the tumor has a papillary, tubular or solid structure, with stratified epithelial cells, and compact tumor aspect. These aspects can be sometimes identified within the same tumor. Cells have cuboid or prismatic shapes, the cytoplasm is usually abundant, eosinophilic, mitotic forms are rare. Cells lie on a fine stroma, with basal membrane. Nuclei are round, hyperchromatic [20] (Fig. 13.1 and 13.2). Tumors can be classified as chromophobic, eosinophilic or clear cell types. Corpora amylacea are common in renal cell tumors of cattle [39].

Fig. 13.1. Cortical adenoma, kidney.

Fig. 13.1

Cortical adenoma, kidney.

Fig. 13.2. Cortical adenoma, kidney.

Fig. 13.2

Cortical adenoma, kidney.

Differential diagnosis between renal adenoma and carcinoma is difficult to make, some structure peculiarities, with obvious malignancy signs, as well as the presence of metastases, being elements that can establish the characteristics of a carcinoma type.

13.1.2. Carcinoma

Renal carcinoma is a malignant tumor, relatively frequent in dogs and cattle, which have been reported in cats, sheep, horses and swine, more frequently in old subjects. In cats, STEINBERG and THOMSON (1994) reported for the first time a bilateral renal tubular carcinoma. Tumor formations were multiple, lobular and confluent, pale, white-gray. Microscopically, neoplasms were formed by pleomorphic cuboid to columnar cells, with discrete fibrovascular tissue. In dogs, the mean age is 8 years, and the male sex is more frequently affected, which has suggested the implication of hormonal factors. Breed cannot influence the incidence of this neoplasm.

Clinical signs are not specific and consist of hematuria, the identification by abdominal palpation of the sublumbar tumor mass, to which the presence of cough due to lung metastases is added. Lung metastases can associate with hypertrophic osteoarthropathy [17]. Laboratory tests can evidence polycytemia, associated with erythropoietin production, anemia and uremia. Tumor cells can be identified in the urinary sediment.

Spontaneous renal carcinomas have also been reported in rats [13] as spherical yellowish-white masses, with red or brown islands. The neoplasm develops metastases on the surface of the diaphragm, liver and lungs, but not in the congeneric kidney or the urinary bladder. Neoplastic cells have a compact or acinar arrangement, in a fibrillar connective stroma. The cytoplasm of neoplastic cells has eosinophilic granulations.

In the German Shepherd breed, the literature [5] mentions the association of renal carcinomas with generalized nodular dermatofibrosis. Histologically, nodules from cutaneous lesions are composed of irregular collagen fibers with very few cells, and inflammatory reaction is discrete. The epidermis is frequently ulcerated. The neoplastic renal lesion is formed by epithelial cells with a compact or tubular-papillary arrangement. Neoplastic cells have abundant, intensely eosinophilic and granular cytoplasm, sometimes with vacuoles. Pleomorphic cells, anisokaryosis and multinucleated cells are found. The mitotic index is low [9, 36].

Macroscopically, the unilateral presence of the tumor is found, and metastases can also be detected in the congeneric kidney, which can create the impression of a primary tumor with bilateral location. Location is in the renal cortex, at one pole of the kidney, under the form of a large spherical tumor that can reach several kg in weight [18]. Smaller neoplasms are delimited from the adjacent renal tissue, producing compression atrophy, and sometimes the carcinoma extends to the neighboring tissues. The tumor can invade the renal pelvis and the urethra or it may reach the renal artery and vein, the vena cava and the aorta. Metastases appear early, being distributed in the renal lymph nodes, lungs, liver, adrenal gland and vertebrae. Secondary tumors may occur in the pancreas, spleen, myocardium, peritoneum, skeletal muscles and bones [17]. Tumors are usually multinodular, soft, due to fibrosis they sometimes have a dense consistency, white, gray or yellowish color, with red or yellow necrotic foci.

Histologically, structure varies within wide limits, which has allowed for a microscopic classification, solid, tubular and papillary carcinoma, and depending on the cell aspect, eosinophilic, basophilic carcinomas, cuboid and columnar cells are distinguished. Mixed neoplasms are frequently found, with different cell shapes within the same tumor. Neoplastic cells may be cuboid, columnar or polygonal, with a small dark nucleus, situated at one pole of the cell. Mitoses are frequent, the cytoplasm is usually acidophilic, renal carcinomas with clear cytoplasm as well as squamous metaplasias also being described. The connective stroma is fine, vascularization is abundant, hemorrhage is frequently found. The histological assessment of the malignancy grade does not always correspond to clinical manifestations. There are tumors with a histological aspect of low malignancy but rapid growth and early metastases in numerous organs [18].

Papillary renal carcinoma has a structure characterized by thin stromal septa with papilliform aspect, covered by small cuboid cells. The cell cytoplasm is basophilic, nuclei are hyperchromatic, with rare mitotic forms. Structure and microscopic characteristics do not show malignancy, but at least in dogs, behavior is that of a highly malignant neoplasm. Thus, vascular invasion and lung metastases are found. Neoplastic cells form tumor emboli that develop in the renal vein, metastases occurring in the lung, brain, heart and epidermis (Fig. 13.3 and 13.4).

Fig. 13.3. Renal cell carcinoma, papillary type.

Fig. 13.3

Renal cell carcinoma, papillary type.

Fig. 13.4. Renal cell carcinoma, papillary type.

Fig. 13.4

Renal cell carcinoma, papillary type.

Tubular renal carcinoma is composed of cuboid or columnar cells, arranged in tubular structures, bordered by fibrous stroma. Tubular structures can sometimes form microcysts. Cell nuclei are heterogeneous in shape, size and staining, and mitoses are frequent (Fig. 13.5 and 13.6).

Fig. 13.5. Renal cell carcinoma, tubular type.

Fig. 13.5

Renal cell carcinoma, tubular type.

Fig. 13.6. Renal cell carcinoma, tubular type.

Fig. 13.6

Renal cell carcinoma, tubular type.

Clear cell renal carcinoma appears as a compact or tubular neoplasm. Tumor cells are large, well delimited, with clear cytoplasm, small, round and hyperchromatic basal nuclei. The connective stroma is fine, with numerous capillaries (Fig. 13.7 and 13.8).

Fig. 13.7. Renal cell carcinoma, clear cell type.

Fig. 13.7

Renal cell carcinoma, clear cell type.

Fig. 13.8. Renal cell carcinoma, clear cell type.

Fig. 13.8

Renal cell carcinoma, clear cell type.

Eosinophilic cell renal carcinoma, in which the cell cytoplasm has eosinophilic granulations, is rarely found. Cells have a compact or trabecular arrangement, abundant, intensely eosinophilic cytoplasm with granulations; nuclei are hyperchromatic, with the occasional appearance of multinucleated cells (Fig. 13.9).

Fig. 13.9. Renal cell carcinoma, pleomorphic eosinophilic type.

Fig. 13.9

Renal cell carcinoma, pleomorphic eosinophilic type.

Nodular dermatofibrosis with renal tumors is a unique and rare familial disease characterized by multiple subcutaneous fibrous nodules, uterine leiomyomas and multiple renal (cyst) adenomas/adenocarcinomas. It is hereditary in German shepherd dogs and appears to be autosomal dominant, associated with an as yet unknown gene localized to canine chromosome 5. It has also been reported in the golden retriever, boxer, German shepherd dog crosses and mongrels, and is seen more frequently in females.

The average age of affected dogs is 8.5 years. The subcutaneous nodules vary from a few millimeters in diameter to large masses greater than 5 cm in diameter. They are well-delineated, can be found anywhere on the body, but are most frequently seen in the limbs, back and head. They produce a distinct bulging, palpable mass in the subcutis, but larger masses may have an ulcerated surface.

In the kidneys, the epithelial tumors are bilateral, multiple and usually cystic. Sizes range from a few millimeters to greater than 10 cm for the solid tumors and greater than 25 cm for the cystic portions.

Microscopic lesions range from hyperplasia to adenoma to adenocarcinoma. Some tumors may only be microscopic and consist of well-differentiated epithelial cells that line tubules or cysts with occasional papillary projections. The neoplasms have tubular, papillary or solid areas, often together in one tumor. Solid areas tend to be more anaplastic; the cells are pleomorphic, ranging from cuboidal to spindle-shaped with pleomorphic nuclei and numerous mitotic figures.

Metastases are present in approximately 50% of the dogs; the most frequent locations of metastases are sternal and renal lymph nodes, but they can also be found in the peritoneum, liver, spleen, lung, pleura and bone [39].

13.1.3. Transitional cell papilloma

Transitional cell papilloma of the renal pelvises is rare, being formed by large cuboid cells, arranged as transitional epithelium, on a fine framework of fibrous connective tissue, with lymphocytic infiltrations. Macroscopically, the tumor appears as a papilliferous nodule, which is prominent in the renal pelvis.

13.1.4. Transitional cell carcinoma

Transitional cell carcinoma can originate from the renal pelvis or the ureter, and it macroscopically appears as papilliferous formations or invasive carcinomas, with a structure identical to transitional cell carcinoma of the urinary bladder. Microscopically, squamous metaplasias and glandular structures can be identified. Transitional cell carcinoma has been described in cats [2, 38].

13.1.5. Squamous cell carcinoma

Squamous cell carcinoma is rarely diagnosed, microscopically having the characteristics of squamous cell carcinoma found in other body regions. Polygonal cells with intercellular bridges and keratinization are identified (Fig. 13.10).

Fig. 13.10. Renal pelvis squamous carcinoma.

Fig. 13.10

Renal pelvis squamous carcinoma.

13.1.6. Undifferentiated carcinoma

Undifferentiated carcinoma is microscopically formed by poorly differentiated, pleomorphic, round, oval to fusiform cells with compact arrangement, with numerous mitoses and either abundant or scant connective stroma. Necrotic and/or hemorrhagic foci appear [40]. Confirmation of their epithelial origin may necessitate immunohistochemical staining with cytokeratin.

Oncocytoma, a rare, usually benign tumor composed of oncocytes. Microscopically, it consists of solid areas, or clusters and nests, or cords and tubules of closely packed, round to oval to polygonal, monomorphic cells, with a brightly eosinophilic granular cytoplasm. Nuclei are round to oval with coarsely stippled chromatin and prominent nucleoli. There may be anisocytosis and anisokaryosis and bi- or multinucleate tumor cells. The diagnosis of renal oncocytoma is based on a positive periodic acid-Schiff reaction, immunoexpression of cytoplasmic cytokeratin, but not vimentin, and abundant mitochondria with stacked cristae. The histogenesis is not known, but these tumors may arise from the collecting ducts (intercalated cells). Oncocytomas are considered benign in humans, but too few cases have been studied in domestic animals to be predictive [39].

13.1.7. Nephroblastoma (embryonal nephroma)

Nephroblastoma or embryonal nephroma is also known as Wilm’s tumor. The origin of this tumor is from undifferentiated metanephric blastema remnants, from the metanephros or its primordium, having the structural characteristics of embryonic kidney. Dysplastic foci or cartilage, bone tissue, smooth or striated muscle tissue can be identified in the tumor structure.

The incidence of nephroblastoma may be considered low, except for swine and chickens. Observations on slaughtered pigs have demonstrated high incidences of nephroblastomas, in England incidence being estimated at 3.5 per 1 million cases, and in USA, at 43.5 cases per 1 million slaughtered pigs, with the mention that in certain geographic areas incidence has been 197 per 1 million cases. In Europe, incidence is lower [17,18].

Nephroblastoma in other species, such as cattle and dogs, is sporadically diagnosed [30, 37].

Incidence in all species is higher in young animals, appearing neonatally in piglets, calves and puppies. Nephroblastomas have even been described in fetuses, without any correlation with breed, but in swine, the male/female ratio is 2:1 and there are data according to which male dogs are also more frequently affected. WATSON et al. (1987) describe nephroblastoma in two 4-month-old female dogs. In both cases, the neoplasm has an irregular aspect under the form of multiple nodules, situated in one kidney, with adherences to adjacent organs and multiple metastases in the lungs and lymph nodes.

Nephroblastoma in old animals is rarer, DILLINGER and CITINO (1987) reporting this neoplasm in an old fox. The authors mention the presence of a nodule 1.5 cm in diameter at the cranial pole of the left kidney, with multiple metastases in both lungs and mediastinal lymph nodes.

Clinical signs are non-characteristic, abdominal dilation is found in dogs and cats on palpation, as well as the presence of a dense fleshy sublumbar formation. Hematuria, weight loss and low appetite may also occur. Signs are generally attenuated due to the functional hypertrophy of the congeneric kidney.

Necropsy shows the presence of a unilateral neoplasm, located at one pole of the kidney, usually being solitary, more rarely multiple or bilateral. It is located in the renal cortex, having a firm consistency, with bosselated, nodular or lobular surface. The tumor is delimited by a fibrous capsule, which penetrates the neoplastic tissue, delimiting lobules. The neoplasm is prominent on the surface of the kidney, it frequently adheres to adjacent tissues, and in the depth, it penetrates the renal medulla and even the renal pelvis. The rest of the renal parenchyma is highly atrophied. Sizes are variable, from several millimeters up to more than 60 cm, and weight can exceed 3 kg. In section, necrotic and/or hemorrhagic foci appear, and cysts, fibrous, cartilaginous and bony nodules, myxomatous masses are detected.

Histologically, a wide variety of structural elements is found. The epithelial component may be dominant, formed by neoplastic tubes and glomerular embryonic structures, delimited by scant connective stroma. Frequently and typically, the neoplasm is composed of epithelial cell islands, with rough tubes and glomerular-like structures. Tubular structures are made up of cuboid or columnar cells, on a basal membrane. The basal membrane is not present in the case of the compact proliferation of neoplastic cells. Sometimes, epithelial structures form cysts in which mucus or parakeratotic formations delimited by squamous metaplasias are found. Mitoses are in a high number. Undifferentiated hyperchromatic epithelial cells can be structured as imaginations, suggesting glomerular embryonic images, without capillaries. The mesenchymal component is discrete in the structure of the neoplasm. In some cases, the mesenchymal tissue acquires neoplastic properties, forming sarcomatous, myxomatous nodules, or developing muscle fibers, bone or cartilaginous nodules. In the case of the presence of a mixed epithelial and mesenchymal tumor structure, with a poor development of tubes and glomerules, prognosis is severe (Fig. 13.1113.13).

Fig. 13.11. Nephroblastoma.

Fig. 13.11


Fig. 13.12. Nephroblastoma.

Fig. 13.12


Fig. 13.13. Nephroblastoma.

Fig. 13.13


Metastases in swine are rare, although nephroblastoma can have impressive sizes. In dogs, metastases are relatively frequent, while in cats and other species they are sporadic. The organs in which metastases may develop are sublumbar, renal, mesenteric and bronchial lymph nodes, the lungs, liver and peritoneum.

The experimental reproduction of nephroblastoma has been carried out in chickens by using oncornaviruses, and in rats by using different carcinogens, among which dimethylnitrosamine.

Thoracolumbar spinal cord tumor of young dogs (nephroblastoma)

A unique embryonal tumor of controversial histogenesis that is intradural and extramedullary in the thoracolumbar spinal column of young dogs. The two proposed tissues of origin of this tumor are neural rests (neuroblastoma) or renal blastema (nephroblastoma).

These are rare tumors, only reported in dogs, between 6 months and 3 years of age; the German shepherd breed is predisposed. The tumors produce an intradural, extramedullary mass of variable size in the thoracolumbar segments (T10–L2) of the spinal cord, with or without associated hyperemia and/or hemorrhage. Occasionally, fronds of proliferating tissue are visible in the dural space, and microscopically, they infiltrate adjacent tissues.

Characteristic histological features are proliferating blast-like cells that form solid nests or line primitive tubular structures, accompanied by embryonic glomerular-like structures consisting of epithelial tufts that project from an epithelial lining into a small lumen. Supporting stroma is sparse, loose and often has a basophilic hue. The number of mitotic figures is variable. The tumor may have villous projections that invade parenchyma and make recurrence in the first 6 months post-surgery likely [39].

13.1.8. Mesenchymal tumors

Primary mesenchymal tumors of the kidney can be benign, such as cortical fibromas, especially in old dogs, then fibrosarcomas, hemangiomas and hemangiosarcomas. Leiomyomas, lipomas and leiomyosarcomas, liposarcomas, respectively, have been more rarely diagnosed.

The macroscopic structure, as well as the microscopic structure of these tumors, is that known for tumors of predilection areas and tissues of the body.

Hemangioma, a benign endothelial cell neoplasm that forms blood-filled channels; hemangiomas are very rare; they are reported to occur in cattle and pigs [39].

Hemangiosarcoma, a malignant tumor of endothelial cell origin that multifocally forms blood-filled spaces; it usually grows through the renal capsule and causes considerable hemorrhage [39].

Fibroma, a benign neoplasm of fibrocytes; fibromas are rare; a report on four cases of fibroma in dogs indicated that they are well demarcated, singular or multiple, and are usually located at the corticomedullary junction [39].

13.1.9. Malignant lymphoma

Malignant lymphoma, previously known in the literature as lymphosarcoma, has renal locations in generalized forms. Cats seem to be the most affected species, in which it has the character of a primary urinary neoplasm, without developing in other organs. Renal lesions in cats frequently occur as bilateral, spherical, white-gray nodules with multiple foci, located in the cortex, having diffuse infiltrative growth [20]. Cats with renal lymphoma react positively for feline leukopenia virus in more than 50% of cases [10].

Histologically, lymphomas are characterized by round, blastic nuclei, little visible cytoplasm, and no supporting stroma. They can be confused with other poorly differentiated neoplasms, histiocytic neoplasms or myeloproliferative diseases, but usually the involvement of lymph nodes, histology/cytology and, if needed, immunohistochemistry make the diagnosis straightforward [39].

13.1.10. Teratoma

Teratoma is a rare tumor, having a complex structural character. Histologically, bone structures, hair follicle tissues, cystic spaces lined by stratified squamous epithelium, sarcomatous and/or carcinomatous islands are found.

13.1.11. Secondary tumors

Secondary tumors appear as renal metastases from neoplasms located in other tissues or organs, having a high incidence in animals. Primary lung neoplasms frequently metastasize in the kidneys. Epithelial tumors that produce renal metastases are pulmonary, mammary, ovarian and prostatic carcinomas, as well as osteosarcomas, mastocytomas and malignant lymphomas. In dogs, primary lung adenocarcinoma with renal metastasis is difficult to differentiate from primary renal adenocarcinoma with lung metastasis [19].

13.1.12. Unclassified tumors

Unclassified tumors are neoplastic growths whose macroscopic aspects and microscopic structures are difficult or impossible to include in one of the mentioned categories. These tumors require a detailed description with all the elements found.

13.1.13. Tumorlike lesions

White spotted kidneys of calves are relatively frequent, being found at slaughter; sometimes, these lesions are involved in the animals’ death. The lesion is known as the “large white kidney”.

Macroscopically, both kidneys usually present small spherical, white-gray nodules, up to 1 cm in diameter, which are prominent on the kidney surface. In section, nodules are white-gray, poorly delimited, tending to penetrate the medulla.

Microscopically, interstitial histiocytic, lymphocytic and plasmacytic infiltration is found. The lesion has the aspect of a reactive process and may regress spontaneously. Etiology has been considered to be of bacterial nature, especially Corynebacterium renale. Macroscopically, the lesion is similar to and may be confused with malignant lymphoma nodules.

Granulomas of feline infectious peritonitis frequently appear in the peritoneal form of the disease, macroscopically being highly similar to malignant lymphoma nodules. Macroscopically, nodules are spherical, 2–10 cm in diameter, of white-gray color, prominent, located under the renal capsule, and in section they have a homogeneous structure and white or gray-white color.

Microscopically, nodules have a granulomatous structure, with the presence of histiocytes, plasmacytes and rare neutrophilic granulocytes.

Hamartoma is a congenital defect, rarely found in kidneys, appearing as a small formation of light color, having a complex structure, cartilaginous tissue, bone and fibrous tissue, without having neoplastic features. There is one hamartoma described in an eight-month-old Holstein heifer. This was a 0.5 cm circumscribed mass at the corticomedullary junction. The mass was composed of poorly organized tubules, possible glomeruloid structures, and disorganized spindle cells in a collagenous stroma. Blood vessels were lined by hypertrophic endothelial cells. An area of loose collagenous stroma with normal blood vessels and normal tubules, partially subdividing the mass, was located between the hamartoma and normal parenchyma. There was fibrosis of adjacent medulla [39].

Telangiectasia, nonneoplastic nodule composed of groups of small, dilated blood vessels lined by simple endothelium. The lesion produces multiple bulging red nodules that tend to aggregate at the corticomedullary junction [39].

Solitary renal cysts have been diagnosed in the majority of domestic animals, frequently in calves, swine and dogs, to which we add lambs, their presence being detected even in abortions.

Macroscopically, cysts are predominant in the renal cortex, with sizes varying from several mm to several cm. Cysts have a clear liquid content, and are delimited by a smooth fibrous wall.

Renal cysts identified in young animals are considered to be congenital anomalies.

Polycystic kidneys represent a much more serious anomaly that causes severe, even fatal uremia, in the case of the involvement of both kidneys. In section, the kidney appears with numerous cysts, delimited by fibrous tissue and renal tissue remnants.

Retention cysts occur following the massive fibrosis of the kidney, and fibrous connective tissue compresses and obliterates the collecting tubes, determining the retention of urine and the dilation of tubes.

Hydronephrosis represents different degrees of dilation of the renal pelvis, following the obliteration of the urinary tract, in the first place of ureters. In chronic forms, the kidney is transformed into a huge cyst, whose wall is a thick fibrous capsule. The main causes of urinary retention can be: urethral stricture due to a congenital abnormality, traumatic lesion or infection; ureteral compression or obliteration by calculi; ureteral twisting and adhesion to the renal pelvis.


Urinary bladder and urethral tumors have a low incidence, except in cattle, in which enzootic hematuria is associated with epithelial and/or non-epithelial neoplasms. In dogs, as well as in cats, incidence is estimated at 0.5–1% of all neoplasms [21, 25, 32, 34]. In all species, these neoplasms predominantly affect adult and old age. In dogs, the majority of urinary bladder and urethral tumors are malignant (97%) and of epithelial origin [20]. These authors mention a 1.95:1 female/male ratio, and the Airedale Terrier, Beagle and Scottish Terrier breeds are more sensitive, while the German Shepherd breed has the lowest incidence [15].

According to SCHWARTZ et al. (1985) [10], urinary bladder tumors in cats are in a proportion of 56% of epithelial nature and malignant, and 36% are mesenchymal, of which 50% are malignant and 8% lymphomas. Urinary bladder tumors in horses have a low incidence and can manifest by hematuria [8].

The etiology of urinary bladder and urethral neoplasms is associated with different industrial chemical substances, such as 2-naphthylamine and benzidine, tryptophan metabolites, chronic irritations, viruses, imperial fern and cyclophosphamides.

Urinary tract tumors have an invasive character with metastases, regression phenomena being exceptional. The presence of secondary tumors is exceptional, and it can be due to neoplasms of organs from the pelvic cavity or the peritoneum, which may implant in the urinary bladder and the urethra.

Histological classification of urinary bladder and urethral tumors:

  1. epithelial tumors: transitional cell carcinoma; squamous cell carcinoma; adenoma; papilloma; adenocarcinoma; undifferentiated carcinoma;
  2. mesenchymal tumors: leiomyoma; leiomyosarcoma; hemangiosarcoma; rhabdomyosarcoma;
  3. lymphoma.

Epithelial tumors represent approximately 80% of all urinary tract tumors (bladder and urethra).

13.2.1. Adenoma

Adenoma is a rare tumor in all species, being characterized by a benign growth of the urinary epithelium, by the mucous metaplasia of the urothelium. It has been occasionally reported in cattle and dogs, in old subjects. Breed and sex are not predisposing factors.

Macroscopically, solitary formations may also occur, with cauliflower-like or multiple shapes, pedunculated, difficult to differentiate from papillomas. Adenomas arise from the mucous glands or by epithelial metaplasia. The metaplastic origin is considered to be the most common. Microscopically, glandular structures appear, separated by connective stroma. Columnar cells are arranged in a single row, and mucus drops appear in their cytoplasm, which confers the aspect of cup-shaped cells. The accumulation of mucus and desquamated cells results in mucous microcysts. Mitoses are exceptional.

13.2.2. Papilloma

Papilloma has an incidence of approximately 17% in cattle and 14% in dogs of all urinary bladder and tract tumors. The tumor usually occurs in adult and old animals, without any breed or sex predisposition.

Macroscopically, papilloma is solitary or multiple, with small sizes, pedunculated or sessile appearance, sometimes invading the mucosa. The first proliferations occur as small projections on the mucosal surface, but proliferation gradually extends, excrescences appear, as well as villosities, with a fibrovascular stalk [18]. In cows, papilliferous growths in the urinary bladder can determine urinary retention that can result in hydronephrosis [29].

Microscopically, well differentiated transitional epithelium is identified, on a basal membrane and a fine connective vascular support. Metaplasias of the proliferated epithelium can be detected, with the appearance of superficial necrosis and hemorrhage. In dogs, papilloma may change into transitional cell adenocarcinoma. The location of papillomas at the level of the bladder neck or in the urethra may cause subocclusion with urinary retention or even hydronephrosis [17] (Fig. 13.14.).

Fig. 13.14. Papilloma, urinary bladder.

Fig. 13.14

Papilloma, urinary bladder.

13.2.3. Carcinoma

Urinary tract carcinomas represent approximately 60% of all primary tumors at this level, in both dogs and cats. The following types can be histologically differentiated: transitional cell carcinoma, which has the highest incidence; squamous cell carcinoma; adenocarcinoma and undifferentiated carcinoma. These carcinoma types can develop under the following forms: papillary carcinoma, which is prominent in the bladder lumen; infiltrating carcinoma, which develops in the bladder wall; carcinoma in situ, when the neoplasm does not exceed the normal limits of the mucosa. Some microscopic preneoplastic aspects of the urinary bladder mucosa should be mentioned, such as a disorganization or an atypical orientation of basal cells, increased cytoplasmic acidophilia, epithelial hyperplasia with marked epithelial thickening in the neoplastic proliferation foci. Epithelial hyperplasia is considered an important precancerous change.

Carcinomas are generally reported especially in old animals, having a higher incidence in dogs, being exceptional in cats and other species. Frequency is higher in males than females, without any breed predisposition.

Transitional cell carcinoma may have a polypoid or sessile papillary growth. Papillary growth is the most frequent, evidenced in the bladder lumen, it resembles papilloma, but it is larger and with a large implantation base. Sometimes, the neoplasm has a cauliflower-like appearance. Infiltrative growth is flat at the surface and frequently ulcerated. Transitional cell carcinoma is the most commonly diagnosed tumor in the urinary bladder of domestic animals. They are most frequent in dogs, occur in cats, and are rare in horses, sheep, goats and pigs. Cattle rarely develop carcinomas spontaneously, but have a high prevalence in geographic regions where enzootic hematuria exists.

This is a neoplasm of older dogs: 9 to 11 years are average reported ages. There is an approximate 2:1 ratio of females to males for bladder neoplasms and neutered males are predisposed. Breeds that may have a greater risk are Airedales, beagles and Scottish terriers, while German shepherd dogs are underrepresented [39].

Transitional cell carcinoma is located on the bladder neck or trigone mucosa, and it can be single or multiple. In most cases, multiple tumors have a papillary growth, variable sizes, some being at the limit of visibility, others occupying the whole bladder lumen. Transitional cells can undergo squamous metaplasia, and metastases are present in 50% of cases in the regional lymph nodes and lungs, and also in the peritoneum and bones (Fig. 13.1513.22).

Fig. 13.15. Papillary and infiltrating transitional cell carcinoma, grade I, urinary bladder.

Fig. 13.15

Papillary and infiltrating transitional cell carcinoma, grade I, urinary bladder.

Fig. 13.16. Papillary and infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.16

Papillary and infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.17. Papillary and infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.17

Papillary and infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.18. Infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.18

Infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.19. Infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.19

Infiltrating transitional cell carcinoma, grade II, urinary bladder.

Fig. 13.20. Infiltrating transitional cell carcinoma, grade III, urinary bladder.

Fig. 13.20

Infiltrating transitional cell carcinoma, grade III, urinary bladder.

Fig. 13.21. Infiltrating transitional cell carcinoma, grade III, urinary bladder.

Fig. 13.21

Infiltrating transitional cell carcinoma, grade III, urinary bladder.

Fig. 13.22

Fig. 13.22

Transitional cell carcinoma with large fat cells, urinary bladder, grade III

Papillary and infiltrating transitional cell carcinoma is the most common variant. Tumors form papillary/cauliflowerlike growths that project into the lumen of the bladder and infiltrate into the muscle layers; these will metastasize. There is a central fibrous stalk of varying thickness that is infiltrated by neoplastic cells. In advanced tumors, there will be multiple secondary or branching villous projections from the main tumor [39]. (Fig. 13.1513.17).

Papillary and noninfiltrating transitional cell carcinoma has a similar luminal-growth pattern, but does not invade the stroma of the stalk or go beyond the lamina propria.

Nonpapillary and infiltrating transitional cell carcinoma is the second most common variant. It appears as a plaque, raised mass or flat nodule. These are often ulcerated and infiltrate into deeper muscle layers. They are a variant most likely to metastasize [39]. (Fig. 13.1813.20).

Nonpapillary and noninfiltrating transitional cell carcinoma (carcinoma in situ) is a flat lesion confined to the surface epithelium. It contains cells that are cytologically malignant and is synonymous with carcinoma in situ. These may or may not be present throughout the entire thickness of the epithelium. It is the least common type seen [39].

Squamous cell carcinoma usually develops under a nodular or sessile form, frequently having prominent margins and an ulcerated center. The macroscopic aspect does not differentiate it from transitional cell carcinoma.

Histologically, squamous cell carcinomas can start as such or as a metaplasia of other forms, including transitional cell carcinoma. This squamous cell carcinoma is common in the distal portion of the urethra in male subjects. The squamous cell carcinoma of the urinary bladder or urethra has the well known characteristic structure of this neoplasm. In the case of metaplastic foci in the structure of other tumor types, these are not considered squamous cell carcinomas (Fig. 13.23.).

Fig. 13.23. Squamous cell carcinoma with distinct keratinization, urinary bladder.

Fig. 13.23

Squamous cell carcinoma with distinct keratinization, urinary bladder.

Adenocarcinomas are in their majority the result of the glandular metaplasia of transitional epithelium, while others are derived from the urinary bladder mucosal glands. The neoplasm has been diagnosed in dogs and cattle, more rarely in cats.

Microscopically, columnar or cuboid cells and mucin secretion characterize glandular formations. The accumulation of mucin in the glands determines cell compression and atrophy, and mucous microcysts sometimes appear (Fig. 13.24.).

Fig. 13.24. Adenocarcinoma, urinary bladder.

Fig. 13.24

Adenocarcinoma, urinary bladder.

Undifferentiated carcinoma is exceptional as a primary tumor and should be considered a neoplasm whose histological structure cannot be classified in one of the types described (Fig. 13.25.).

Fig. 13.25. Undifferentiated carcinoma, spindle cell type, urinary bladder.

Fig. 13.25

Undifferentiated carcinoma, spindle cell type, urinary bladder.

13.2.4. Mesenchymal tumors

Mesenchymal tumors represent approximately 20% of all urinary tract neoplasms. The most frequently diagnosed histological forms are leiomyomas and leiomyosarcomas, 12%, followed by hemangiomas and hemangiosarcomas, 6%, and fibromas and fibrosarcomas, 2%. Rhabdomyomas and rhabdomyosarcomas have been exceptionally diagnosed [18] (Fig. 13.27. and 13.28.).

Fig. 13.27. Hemangioma, urinary bladder.

Fig. 13.27

Hemangioma, urinary bladder.

Fig. 13.28. Hemangiosarcoma, urinary bladder.

Fig. 13.28

Hemangiosarcoma, urinary bladder.

Leiomyoma originates from the urinary bladder muscularis, under the form of well delimited white nodules. Usually, nodules are multiple, being located in the proximity of the urinary bladder neck. Microscopically, nodules have a typical smooth muscle structure.

Leiomyosarcoma, as well as its metastases, have been exceptionally diagnosed. In a 10-year-old German Shepherd dog, SEELY et al. (1978) diagnosed urinary bladder leiomyosarcoma with metastases in the lung, liver, intestine and kidney. Macroscopically, large confluent nodules were present in the thickness of the urinary bladder wall, from the serosa to the mucosal surface, with infiltrative growth.

Microscopically, the neoplasm showed high cell pleomorphism, with atypical mitoses, striations were identified in the eosinophilic cytoplasm, and electron microscopy revealed myofilaments. Urinary bladder leiomyosarcoma in cats is extremely sporadically reported by the literature [3] (Fig. 13.26.).

Fig. 13.26. Leiomyosarcoma, urinary bladder.

Fig. 13.26

Leiomyosarcoma, urinary bladder.

Fibroma develops from the subepithelial connective tissue, it appears as a solitary nodule, with macroscopic and microscopic structure typical of fibroma. The tumor is found in old dogs.

Fibrosarcoma, as a primary tumor, is found in dogs. The uni- or multifocal infiltrative growth, the macroscopic appearance, and the well known microscopic structure of this neoplasm accompanied by metastases, establish positive diagnosis.

Botryoid rhabdomyosarcoma is a cluster-shaped tumor, located in the urinary bladder and occasionally in the urethra of young dogs, found in large breeds, especially St. Bernard and Danish Dog. The neoplasm is more common in dogs under the age of 18 months; it is supposed to develop from embryonic myoblastic remnants [35]. Macroscopically, the tumor develops in the bladder trigone area and in the bladder neck. It has infiltrative growth, and it can metastasize. Microscopy shows a mixed structure of fusiform and pleomorphic cells in a garland pattern and/or multinucleated cells. Striations are detected in the cell cytoplasm [17].

Mixed tumors, with epithelial and mesenchymal elements have been diagnosed under the form of carcinoma, carcinohemangioma and carcinoleiomyosarcohemangioma, adenohemangioma and papillohemangioma. These complex neoplastic forms have been diagnosed in particular in cattle.

Malignant lymphoma in the urinary tract structures is less reported by the literature, compared to other tissues or organs (heart, uterus, etc.). In horses, SWEENEY et al. (1991) describe large gray masses that infiltrate the urinary bladder, vagina, uterus and large ligaments. Histology shows a massive infiltration of young lymphocytes, with basophilic cytoplasm, numerous mitoses, bizarre cells with 3 nuclei.

13.2.5. Secondary tumors

Secondary tumors appear in the urinary bladder and the urethra as a result of metastases of tumors from adjacent organs (prostate, rectum and uterus) and more rarely of neoplasms from other organs [23] (Fig. 13.29. and 13.30.).

Fig. 13.29. Urinary bladder adenocarcinoma.

Fig. 13.29

Urinary bladder adenocarcinoma.

Fig. 13.30. Urinary bladder adenocarcinoma, lung metastasis.

Fig. 13.30

Urinary bladder adenocarcinoma, lung metastasis.

13.2.6. Urinary bladder tumors in bovine enzootic hematuria

Enzootic hematuria is a syndrome found in cattle, also reported in sheep, characterized by persistent hematuria and anemia, accompanied by hemorrhage and neoplasms in the urinary bladder and urethra. More than 90% of subjects with enzootic hematuria present urinary tract neoplasms.

Enzootic hematuria has an endemic evolution in certain areas, as a result of the chronic consumption of the fern species Pteridium aquilinum subsp. aquilinium, with eight varieties, and Pteridium aquilinum subsp. caudatum, with four varieties. In Australia, the Cheilandes sieberi fern is associated with the presence of enzootic hematuria. In Kenya, the high incidence of the urinary bladder tumor in Zebu cattle is not associated with fern ingestion or enzootic hematuria [17]. Enzootic hematuria has been found to occur in cattle grazing on arid soils or fed with hay from these soils; the disease has also been reported in Nepal [11]. The mentioned fern species and varieties contain toxic substances from the thiaminase group, different carcinogens, such as quercetin, shikimic acid, prunasin, ptaquilo side, aquilide A, etc., as well as a hemorrhagic factor with unknown structure [11, 17]. Lately, the possible role of an oncogenic virus has been discussed, such as esophageal and forestomach papillomaviruses. However, the role of carcinogenic factors such as ptaquiloside is a certainty. By using ptaquiloside extracted from fern rhizomes and leaves, hemorrhagic, then neoplastic lesions were reproduced in both cattle and laboratory animals [22].

Experimentally, rats receiving feed rations that contained 50% fern (Pteridium aquilinum) manifested erythrocytopenia, thrombocytopenia and leukocytopenia. Subjects developed intestinal adenomatous polyps and neoplastic proliferations of Paneth cells [27].

Affected cattle are aged between 4 and 12 years, and younger animals develop a subclinical form. The appearance of clinical signs is variable, but earlier and more serious forms are found in cattle brought from other regions. Hematuria has an insidious onset, is characterized by a slow but progressive development, with remissions whose duration varies from several days to several months. The intensity of hematuria is not directly correlated with urinary bladder lesions; some lesions, especially neoplastic, can manifest by the discrete presence of blood in urine, which frequently passes unobserved by the owner. In a study performed in an endemic region with enzootic hematuria, some slaughtered control bovines, without hematuria, presented macroscopic petechial lesions and/or papilliferous growths on the surface of the bladder mucosa [1, 24].

Macroscopically, lesions start with petechiae and suffusions in the mucosa of the urinary bladder, urethra, ureters and renal pelvis. Concomitantly or in more advanced stages, small epithelial proliferations occur, which make the mucosal surface irregular, or they appear as polyps, nodules or large neoplastic masses, especially on the bladder floor, towards the cranial pole and/or the bladder neck. Proliferative lesions frequently appear with ulcerohemorrhagic lesions, sometimes on extensive surfaces. Tumors occur as fibropapillomas, solitary or multiple, polypous or sessile proliferations, with a large base, sometimes with mucous aspect.

Histologically, extensive erythrocyte and lymphocyte infiltration is found. In incipient forms, epithelial cells are perpendicular to the basal membrane, with poorly colored cytoplasm and large vesicular nuclei. The presence of cavernous hemangiomas, with hyperplastic endothelium, may be detected. Fibropapillomatous proliferations show multiple prolonged ramifications, with fine, highly vascularized connective stroma. Epithelium is formed by tall, elongated cells, with large obvious nuclei. Sessile, cauliflower-like proliferations are covered by epithelium with anarchically arranged cells, with clear, vacuolized cytoplasm, large nuclei with bizarre shapes. Superficial epithelium penetrates as digitiform structures in the chorion, forming cell islands. In the depth, in the chorion and even in the muscle area, cell bands with a solid carcinoma appearance or pseudoacinar arrangement with a large lumen containing basophilic material occur. Epithelial metaplasia of urinary type can be found in multistratified or even squamous epithelium (Fig. 13.23, 13.2913.32).

Fig. 13.31

Fig. 13.31

Carcinoma in situ, urinary bladder, cow

Fig. 13.32

Fig. 13.32

Infiltrative carcinoma, urinary bladder, cow

Electron microscopically, superficial cells have spherical mitochondria, without cristae, numerous secondary lysosomes, some of which are gigantic, microtubules arranged in a network, and concentric endoplasmic reticulum. The luminal surface of superficial cells show microvilli specific for tumor processes. The basal membrane thickness is non-uniform, with discontinuities and the disjunction of the membrane from basal cells, the enlargement of intercellular spaces. Blood capillaries in the chorion have an unevenly thickened basal membrane, endothelial activation images (large cells with voluminous nuclei) and wall ruptures. Epithelial cells from tumor proliferations have an irregular outline, due to numerous filiform expansions; the high number of desmosomes and large intercellular spaces, filled with fibrillar matrix, should be remarked. The cytoplasm is dense, granular, homogeneous, with rare vesicular structures. In the proximity of the plasmalemma and in extensions, the cytoplasm is dense due to keratinization [1].

13.2.7. Tumorlike lesions

Polypoid cystitis is reported in many species and is seen most often in younger male dogs. This form of cystitis is often attributed to chronic irritation from urinary tract infection or uroliths resulting in mucosal polypoid projections of urothelium. Grossly, the bladder mucosal surface is elevated by multiple nodular to polypoid lesions, 2–3 cm in diameter, that protrude into the lumen. The microscopic features are edema, congestion, connective tissue proliferation, transitional cell epithelial hyperplasia covering a core of proliferating connective tissue, and a variable inflammatory cell infiltration with areas of ulceration and hemorrhage. In cattle, the polyp may undergo mucoid degeneration and there may be metaplasia of epithelium to a mucus-secreting glandular type [39].

Polypoid eosinophilic cystitis is a relatively common lesion in the urinary bladder of dogs and has been observed in cattle. Dogs present with recurrent hematuria that may necessitate exploratory surgery, during which a discrete mass is excised from the bladder. A nodule of fibrous tissue confined to the lamina propria and covered by hyperplastic transitional epithelium characterizes the lesion. The fibrous nodules will have areas devoid of inflammation. Eosinophils are a distinctive feature. Some lesions contain neutrophils and lymphocytes; there may be lymphoid nodules [39].

Polyp, a pedunculated or sessile nodule of fibrous tissue covered by nonneoplastic urothelium. The urothelium is hyperplastic and/or ulcerated. The fibrous mass may have concurrent inflammation. There is probably a continuum between polyps, polypoid cystitis and eosinophilic cystitis [39].

Metaplasia. The two forms of metaplasia usually occur with cystitis and hyperplasia of transitional epithelium.

Glandular metaplasia (cystitis glandularis). The lesion is subjacent to hyperplastic urothelium. The acini are lined by columnar epithelial cells and goblet cells that resemble intestinal epithelium

Squamous metaplasia, transitional epithelium that has converted to squamous epithelium. There may be one or more foci and the adjacent urothelium is hyperplastic [39].

Brunn’s nests, solid transitional cell nests of various sizes within the lamina propria that are near to or continuous with the urothelium. The cells are uniform and well differentiated, with a moderate amount of cytoplasm, and appear as hyperplastic transitional epithelial cells. Concurrent cystitis, edema, and fibrosis are often present. Brunn’s nests may undergo cystic change resulting in a central lumen lined by layers of urothelial cells. The isolated nests are probably the result of tangentially cutting hyperplastic urothelium. This change can also occur in the renal pelvis [39].


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List of Figures 13.1-13.32

  • Fig. 13.1 Cortical adenoma, kidney. *)
  • Fig. 13.2 Cortical adenoma, kidney. *)
  • Fig. 13.3 Renal cell carcinoma, papillary type. *)
  • Fig. 13.4 Renal cell carcinoma, papillary type. *)
  • Fig. 13.5 Renal cell carcinoma, tubular type.
  • Fig. 13.6 Renal cell carcinoma, tubular type. *)
  • Fig. 13.7 Renal cell carcinoma, clear cell type. *)
  • Fig. 13.8 Renal cell carcinoma, clear cell type. *)
  • Fig. 13.9 Renal cell carcinoma, pleomorphic eosinophilic type.
  • Fig. 13.10 Renal pelvis squamous carcinoma. *)
  • Fig. 13.11 Nephroblastoma. *)
  • Fig. 13.12 Nephroblastoma. *)
  • Fig. 13.13 Nephroblastoma. *)
  • Fig. 13.14 Papilloma, urinary bladder.
  • Fig. 13.15 Papillary and infiltrating transitional cell carcinoma, grade I, urinary bladder. *)
  • Fig. 13.16 Papillary and infiltrating transitional cell carcinoma, grade II, urinary bladder. *)
  • Fig. 13.17 Papillary and infiltrating transitional cell carcinoma, grade II, urinary bladder. *)
  • Fig. 13.18 Infiltrating transitional cell carcinoma, grade II, urinary bladder. *)
  • Fig. 13.19 Infiltrating transitional cell carcinoma, grade II, urinary bladder. *)
  • Fig. 13.20 Infiltrating transitional cell carcinoma, grade III, urinary bladder. *)
  • Fig. 13.21 Infiltrating transitional cell carcinoma, grade III, urinary bladder. *)
  • Fig. 13.22 Transitional cell carcinoma with large fat cells, urinary bladder, grade III. *)
  • Fig. 13.23 Squamous cell carcinoma with distinct keratinization, urinary bladder.
  • Fig. 13.24 Adenocarcinoma, urinary bladder.
  • Fig. 13.25 Undifferentiated carcinoma, spindle cell type, urinary bladder. *)
  • Fig. 13.26 Leiomyosarcoma, urinary bladder. *)
  • Fig. 13.27 Hemangioma, urinary bladder.
  • Fig. 13.28 Hemangiosarcoma, urinary bladder. *)
  • Fig. 13.29 Urinary bladder adenocarcinoma.
  • Fig. 13.30 Urinary bladder adenocarcinoma, lung metastasis.
  • Fig. 13.31 Carcinoma in situ, urinary bladder, co.
  • Fig. 13.32 Infiltrative carcinoma, urinary bladder, co.



Courtesy of W.H.O.

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