Unusual cutaneous carcinoma with features of small cell (oat cell-like) and squamous cell carcinomas. A variant of malignant Merkel cell neoplasm.

Three unusual primary neoplasms in the skin that occurred in elderly patients (64, 77, and 69 years of age) are presented. Two histologic components were found in each of the three neoplasms, one being small cell or oat cell-like carcinoma and the other squamous cell carcinoma. Study by electron microscopy revealed neurosecretory granules, though few, in the small cell component. The lack of clinical evidence of oat cell carcinoma elsewhere, the autopsy finding of two histologic components in one patient, and the findings by conventional and electron microscopy lead us to conclude that these three neoplasms are primary in the skin and of Merkel cell origin. We suggest further that small cell carcinoma of the skin represents a poorly differentiated counterpart of trabecular carcinoma. The spectrum of malignant Merkel cell neoplasm is, therefore, expanding. Two of our three patients died of their neoplasms 2 and 2 1/2 years, respectively, after the initial diagnosis.