[Primary neuroendocrine carcinoma of the skin: histologic, immunohistochemical and ultrastructural study of a case with highly aggressive biological behavior].

We report a histological, immunohistochemical and ultrastructural study of a case of neuroendocrine carcinoma of the skin, which occurred in a 52 years old woman in the dermal, subcutis and soft tissues of the left buttock. Clinically this neoplasm, which was related to intramuscular injections and a to a following abscess, had rapidly reached unusual dimension compared with other cases of neuroendocrine carcinoma of the skin reported in the literature. The patient died three months after presentation with distant metastases. A variable percentage of the neoplastic cells was positive for low molecular weight cytokeratins (CK), neurofilaments (NF), neuron specific enolase (NSE) and occasionally for vaso-intestinal polypeptide (VIP). Ultrastructural investigations showed two types of neoplastic cells, identified for some features of the nucleus and of the cytoplasm; these two groups of cells are, in our opinion, related to different stages of cellular development. Our results, in agreement with some observations reported in the literature, give evidence of a possible origin of neuroendocrine carcinoma of the skin from an undifferentiated cell which is capable of neuroendocrine or ectodermal differentiation.