Cutaneous metastases as an initial manifestation of visceral well-differentiated neuroendocrine tumor: a report of four cases and a review of literature.

Well-differentiated neuroendocrine tumors metastasize to the skin uncommonly, and only 35 cases are reported in the literature. In only five of these patients, cutaneous metastases were the presenting symptom of malignancy; herein, we report four such cases. Two patients were female and two male, aged 50-74 years (mean: 64.5 years), each with a solitary painless, slowly enlarging, non-ulcerated cutaneous nodule of 3-12 months duration (mean: 9 months). The lesions were on the scalp (n = 3) and trunk (n = 1), and ranged in greatest dimension from 0.5 to 2.5 cm. The distinction from other microscopically similar entities, and the interpretation of origination from gastrointestinal, pancreatic or respiratory system primaries, was made clinically, or was based on the morphological features and the immunohistochemical profile. One patient died of the disease progression after 36 months whereas two patients are alive with significant disease progression after 24 and 60 months. Metastatic neuroendocrine tumor should be considered in the differential diagnosis of cutaneous tumors with neuroendocrine morphology even in patients with no known history of visceral malignancy.