Small cell carcinoma of the skin "non-Merkel cell type"

An 81-year-old Japanese woman developed small cell carcinoma of the skin, which was different from trabecular carcinoma or neuroendocrine carcinoma of the skin. The tumor was composed of spindle-shaped or fusiform cells with scanty cytoplasm and numerous mitoses. The tumor cells were arranged in a streaming pattern and not in anastomosing trabecular fashion at all. No granules were detected by Grimelius' stain either. Immunoperoxidase staining for neuron specific enolase (NSE) did not reveal any activity. Ultrastructural study showed scanty organelles in the cytoplasm which contained a few round mitochondria, rough endoplasmic reticulum, and free polysomes. Occasionally, filamentous bundles, desmosomes, and intracytoplasmic canaliculi were recognized in the cytoplasm, but neurosecretory granules were not found throughout the cytoplasm. Electron microscopic features suggest that this tumor originated from the embryonal stratum germinativum. The present tumor can be distinguished from trabecular carcinoma or neuroendocrine carcinoma of the skin, and may be regarded as "small cell carcinoma" of the skin.