Primary carcinoid tumor of the skin: a literature review.

Primary carcinoid tumor of the skin (PCTS) is an uncommon indolent neoplasm, with 10 cases described in the literature. The tumors affect patients in the sixth to ninth decades of life (mean = 66.3 years) with an equal gender distribution and predilection for the head and trunk. They present as slowly enlarging nodules of variable duration, ranging from 1 to 60 years (mean = 11.4 years). PCTS is characterized by architectural, cytomorphologic, ultrastructural, and immunohistochemical features typical of a low-grade neoplasm with neuroendocrine differentiation. PCTS typically follows a benign clinical course and therefore has to be distinguished from cutaneous metastases of visceral carcinoid tumors, which herald dissemination of malignancy and poor prognosis. While the distinction from other histologically similar entities can be achieved by histopathological examination, PCTS can be distinguished from a visceral metastasis only by a judicious clinicopathologic correlation. Herein we describe the clinical presentation, histological appearance, and management of these tumors.