Case report of neuroendocrine carcinoma of the skin, histochemical and electron microscopic study.

A rare case of neuroendocrine carcinoma of the skin in a 83-year-old male Japanese was reported. Histological, electron microscopical and cytological studies were performed on the surgically removed tumor tissue and the cultured tissue. The tumor occurred at the junction of the dermis and subcutaneous tissue of the right elbow, and spread to the right brachial region and axilla. Histologically, the tumor consisted mostly of small anaplastic cells, closely resembling lymphocytes. They showed a characteristic uniformity without rosette or trabecular formation in the usual histological sections, but an epithelial-like arrangement of tumor cells was readily observable both in the tissue culture and imprint preparations. Grimelius' stain was weakly positive in the periphery of the cytoplasm. Neuron Specific Enolase (NSE) activity was high both in the serum and in the tumor mass. No gastro-entero-pancreatic hormones were detected. Electron microscopically, membrane-bound granules of neurosecretory type, 90 to 170 nm in diameter were observed in the cytoplasm. These granules were characteristically distributed along the periphery of cytoplasm beneath the plasma membrane and in clusters in the cell processes. The tumor cells had sparse rudimentary desmosome-like junctions and a few cytoplasmic finger-like projections. Either a neurogenic or APUD cell origin of the tumor was suspected. The serum NSE value, suggesting to be a neurogenic origin before the histological examination in the present case, is considered to be a valuable marker substance for screening and therapeutic monitoring of neurogenic tumors.