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Holzheimer RG, Mannick JA, editors. Surgical Treatment: Evidence-Based and Problem-Oriented. Munich: Zuckschwerdt; 2001.

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Surgical Treatment: Evidence-Based and Problem-Oriented.

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Cystic tumors of the pancreas

, M.D., , M.D., and , M.D.

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Cystic tumors of the pancreas are relatively uncommon, accounting for 10% of cystic lesions of the pancreas, and 1% of pancreatic neoplasms (1). Mucinous cystic neoplasms (MCN), serous cystadenomas, and intraductal papillary mucinous tumors (IPMT) comprise more than 90% of the primary cystic neoplasms of the pancreas, but other pathologic entities with cystic appearance are also known (table I). Accurate recognition of these lesions is important because of their ability to masquerade as pancreatic pseudocysts and their high cure rate following surgical treatment.

Table I. Cystic neoplasms of the pancreas: MGH Series 1978–1998.

Table I

Cystic neoplasms of the pancreas: MGH Series 1978–1998.

Differential diagnosis

Patient evaluation after discovery of a cystic lesion of the pancreas should initially be directed towards exclusion of a pancreatic pseudocyst(2). As opposed to cystic neoplasms, pseudocysts lack an epithelial lining, and represent collections of pancreatic secretions which have extravasated from a duct disrupted by inflammation or obstruction. Patients with pseudocysts often have a history of acute or chronic pancreatitis, while most of those with cystic tumors lack such antecedent factors. Radiographic characteristics which favor a diagnosis of pseudocyst over cystic neoplasms include: lack of septae, loculations, solid components, or cyst wall calcifications on CT; hypovascularity on angiography; and communication between the cyst and the pancreatic ductal system on ERCP. Aspiration of pseudocyst contents reveals high levels of amylase in practically all cases. When unable to establish the nature of a cystic lesion, it is better to resect a pseudocyst than to mistakenly observe or internally drain a cystic neoplasm, which could allow tumor progression to unresectability, metastasis, and death.

If a diagnosis of pancreatic pseudocyst can be ruled out, evaluation should subsequently focus on identifying those tumors which require surgical resection due to actual or potential malignancy. As opposed to ductal adenocarcinoma, cystic neoplasms with malignant potential are slow-growing, and favorable prognosis have been reported even in the setting of malignant degeneration. Tumors with malignant potential include MCN, IPMT, papillary cystic neoplasms, and cystic islet cell tumors. Serous cystadenomas, in contrast, are almost universally benign. The diagnostic examination of choice is the spiral CT with intravenous contrast enhancement, allowing tumor localization and sometimes discrimination of serous cystadenomas from other neoplasms. Analysis of cyst fluid can also aid in the evaluation of cystic neoplasms (3,4) (table II). Elevated fluid amylase levels are characteristic of > 95% of pseudocysts, and thus a normal amylase can be used to exclude a pseudocyst. Fluid levels of carcinoembryonic antigen (CEA) can be elevated in a variety of cystic lesions including MCN, IPMT and some pseudocysts, but is always low or normal in serous cystadenomas. If accurate diagnosis is not possible despite all efforts, resection rather than observation is preferred. A summary of some of the distinguishing features of the most common cystic tumors of the pancreas is presented intable III and discussed below.

Table II. Cyst fluid analysis in cystic tumors of the pancreas.

Table II

Cyst fluid analysis in cystic tumors of the pancreas.

Table III. Characteristics of cystic neoplasms of the pancreas.

Table III

Characteristics of cystic neoplasms of the pancreas.

Tumor characteristics and treatment

Mucinous Cystic Neoplasms

MCN are the most frequently encountered cystic tumors of the pancreas, accounting for 45–50% of tumors (table I). MCN display a clinical and histological spectrum ranging from clearly benign to frankly malignant tumors. Accurate diagnosis requires examination of extensive samples of cyst epithelium and mandates complete surgical resection and not just simple biopsy(5). Current pathologic classification distinguishes between benign, borderline or malignant (cystadenocarcinomas) tumors based on their maximal degree of dysplasia(6). This classification scheme correlates to patient prognosis, and suggests that these tumors should be treated as premalignant lesions with eventual evolution to aggressive behavior if left untreated.

MCN occur primarily in females (80%), with a mean age of 55 years, who complain primarily of abdominal pain or palpable mass. Symptoms such as weight loss and jaundice are more common with malignant tumors. Today, with the more liberal application of CT scanning in medical evaluations, an increasing percentage of tumors are being diagnosed while asymptomatic.

Grossly, MCN consist of multiloculated tumors with smooth, glistening surfaces which develop predominantly (66%) in the body or tail of the pancreas. Cysts range in size from 2 to 26 cm in maximum diameter, large tumors being more often malignant than smaller ones. The cysts are filled with viscous mucous material, and cyst walls are dense and fibrous with occasional calcification. Abdominal ultrasound or CT successfully demonstrates many of these characteristics. CT may also allow identification of solid components associated to cystic elements, features of borderline or malignant tumors but not of benign variants. Pancreatography rarely demonstrates cyst communication with pancreatic ducts, but frequently shows duct displacement by mass effect or ductal obstruction in 25% of malignant MCN. When performed, cyst fluid analysis generally reveals high viscosity, elevated tumor markers (CEA), and may show malignant cytology (table II).

Due to their inherent potential for malignancy, surgical resection is advocated for all MCN. In most instances this requires distal pancreatectomy with splenectomy, but pancreaticoduodenectomy is indicated for tumors of the head of the pancreas. More limited resections, such as enucleation, are not recommended owing to the risks of fistula formation and inadequate tumor margins(7). Resectable metastases should be excised with the primary tumor based on long-term cures reported after such procedures. Five-year survivals are excellent (> 95%) for benign or borderline MCN, and long-term survivals are also expected for 50–75% of fully-resected malignant tumors. In our experience, unresectable malignant tumors carry as bad a prognosis as unresected ductal adenocarcinoma(1).

Serous cystadenomas

Serous cystadenomas, also known as microcystic adenomas, are the second most common cystic tumors of the pancreas (table I). The clinical presentation of serous cystadenomas is similar to that of MCN, occurring mostly in females (80%) with a mean age of 63 years, and localized primarily in the body or tail of the pancreas (50–70%)(8). An association withvon Hippel-Lindau disease has also been noted. Most patients present with vague abdominal pain or discomfort, but a significant number can present with a palpable mass when the tumor has attained a large size (range: 1–25 cm). Increasingly, incidental asymptomatic tumors are being detected during evaluation for other unrelated conditions.

Macroscopically, serous cystadenomas consist of well-circumscribed pancreatic neoplasms, which on cross-section show numerous tiny cysts separated by delicate fibrous septae giving them a honeycomb appearance. The cysts are filled with clear watery fluid, and are often arranged around a central stellate scar which may be calcified. The pathognomonic image by CT scan is that of a spongy mass with a central “sunburst” calcification, but occurs in a minority of patients (10%). Endoscopic ultrasound may allow better resolution of the honeycomb structure than CT. Macrocystic variants are known which may be indistinguishable from MCN. Hypervascularity may be demonstrated by angiography, and some tumors have presented with intraabdominal hemorrhage. Cyst fluid analysis characteristically reveals low viscosity, low levels of CEA, and negative cytology (table II).

As opposed to MCN, the vast majority of serous cystadenomas are benign tumors. Very rare case reports of serous cystadenocarcinomas exist, but constitute much less than 1% of known cases(9). Surgical resection is the treatment of choice for symptomatic lesions, and may require a Whipple procedure or distal pancreatectomy according to anatomic location. Distal pancreatectomy may be done without splenectomy given the absence of malignant potential. Alternatively, small serous cystadenomas may be safely observed if asymptomatic. Observation carries a very small risk of malignant degeneration. Additionally, the natural history of some serous cystadenomas is of continued growth which may lead to complications such as hemorrhage, obstructive jaundice, pancreatic insufficiency, or gastric outlet obstruction(8). For these reasons and given the safety of pancreatic resection in specialized centers today, we advocate resection of most serous cystadenomas if the patient's condition allows it.

Intraductal papillary mucinous tumors

Since their initial description in 1982, more than 200 cases of IPMT have been reported in the English literature (table I). A variety of terms have been applied in reference to these neoplasms and include: mucinous ductal ectasia, intraductal mucin-producing tumor, intraductal cystadenoma, pancreatic duct villous adenoma, intraductal papillary neoplasms, and others(10). Some pathologists suggest that IPMT are only a variant of MCN, but establishment of a relationship between these tumors awaits further investigation.

IPMT represent papillary neoplasms within the main pancreatic duct which show mucin hypersecretion that often leads to duct dilatation and/or chronic obstructive pancreatitis. IPMT are considered premalignant pancreatic lesions, and histologically may demonstrate areas ranging from hyperplasia to carcinoma within a single tumor(11). Although extensive longitudinal intraductal growth can be observed, they are slow to invade periductal tissues radially and slow to metastasize.

Most reported case series demonstrate that IPMT occur primarily in males with a mean age of 65 years, in contrast to the female predominance in MCN(12). Patients frequently present with abdominal pain or pancreatitis, and may be found to have a past history of recurrent pancreatitis. The disease is most commonly localized to the head of the pancreas, but may occur at any site along the pancreatic ductal system. Duct dilatation is often impressive and may mimic MCN on CT scan imaging. Evaluation by ERCP typically shows a patulous ampulla of Vater with extruding mucus, which is often diagnostic for IPMT. Other findings during pancreatography include: main duct dilation, filling defects (viscid mucus), and communication between cystic areas and the main pancreatic duct.

Adequate treatment of IPMT requires pancreatic resection, which successfully relieves symptoms and prevents tumor progression to invasive carcinoma. Simpler procedures such as sphincterotomy, stenting, and clearance of intraductal mucus may partially treat symptomatology but do not address the malignant potential of these tumors. Pancreaticoduodenectomy is the treatment of choice for most patients given the predominance of IPMT in the head of the pancreas, but distal pancreatectomy is indicated for lesions in the body or tail of the gland. Intraoperative frozen sections are necessary to confirm negative duct resection margins, and mandate extended resection if positive. When disease involves the entire ductal system, total pancreatectomy is the only curative surgical option. Recurrence in the duct of the pancreatic remnant has not been reported after curative resection, and 5-year survivals greater than 80% are common for noninvasive tumors (10,12).


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Copyright © 2001, W. Zuckschwerdt Verlag GmbH.
Bookshelf ID: NBK6998


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