Small-cell neuroepithelial tumor of skin: a Merkel-cell neoplasm?

Two patients with small-cell undifferentiated neuroepithelial tumors of skin are reported. The histologic and ultrastructural features of this neoplasm are presented. Characteristic membrane-bound, dense-core neurosecretory granules were seen in the cytoplasm of the tumor cells in both cases. The literature is reviewed in regard to the clinical behavior of these lesions and their possible cell of origin. Dermatologists should be aware of these tumors because they may require electron microscopy for accurate diagnosis. The tumors should be treated aggressively to minimize the chance of local recurrence and nodal or visceral metastases.