In summary, carcinoma is the most frequent cancer that metastasizes to the skin; lung cancer in men and breast cancer in women. Clinically distinctive patterns of cutaneous metastasis of epithelial origin include alopecia neoplastica, pulsatile nodules, Sister Mary Joseph's nodules, morpheaform, and cellulitis-like lesions. Biopsying these lesions reveals adenocarcinoma, squamous cell carcinoma, or anaplastic carcinoma. The type of histologic pattern seen can be a clue to the organ of origin giving rise to the cutaneous metastasis. Skin that is damaged allows for circulating malignant cells, often of epithelial or leukemic origin, to lodge and proliferate locally (inflammatory oncotaxis). The commonest form of leukemia to affect the skin of elderly males is chronic lymphocytic leukemia. However, when leukemia involves the mucous membranes, acute myeloid leukemia (acute monocytic and acute myelomonocytic leukemia) is the most likely diagnosis. When papules, nodules, or plaques develop on the head, neck, or torso in a middle-aged male accompanied by lymphadenopathy, there must be a high index of suspicion that these lesions are metastatic lymphomatous deposits. Definitive histologic diagnosis on a skin biopsy specimen is difficult. In this situation, it is best to rely on histologic patterns seen in lymphoid tissue along with cellular marker studies. An elderly patient having bone pain, anemia, elevated blood calcium level, and renal failure along with purplish or skin-colored nodules and plaques on the trunk has a good chance of having multiple myeloma. Biopsying these lesions is most certain to reveal atypical plasma cells, and blood immunoelectrophoresis will demonstrate characteristic monoclonal gammopathy. There are two malignancies seen in children under 3 years of age that often times affect the skin in a characteristic fashion. Letterer-Siwe disease, which is distinguished from other histocytic disorders by its cell of origin, the Langerhans cell, clinically shows maculopapular and erosive lesions distributed in a seborrheic pattern. Neuroblastoma derived from cells of the neural crest demonstrates clinically widespread bluish papulonodules. Kaposi's sarcoma, a multifocal vascular malignancy, has a wide spectrum of clinical expression. Those patients who are immunocompromised secondary to concomitant disease or immunosuppressive therapy are more susceptible to a disseminated fulminant course accompanied by opportunistic infection. In conclusion, although specific signs of internal malignancy are less common than nonspecific ones, they are just as important; if the clinician managing the cancer patient is familiar with these clues to internal disease, proper patient management will ensue.(ABSTRACT TRUNCATED AT 400 WORDS)