Merkel cell carcinoma: a distinct lesion of the eyelid.

Merkel cell carcinoma (trabecular cell carcinoma) is a rare, distinct, primitive, neuroendocrine malignancy of the skin, usually affecting elderly patients. It develops from Merkel cells and nearly one out of every 10 Merkel cell carcinomas occurs in the eyelids and periocular region. The tumor manifests itself clinically as a bulging lesion near the lid margin, painless, reddish colored with teleangiectatic blood vessels on the surface. Histologically, the tumor can mimic malignant lymphoma, undifferentiated melanoma, sebaceous carcinoma or cutaneous metastases of pulmonary microcytoma. Immunohistochemical studies with antibodies to neuron-specific enolase, cytokeratins and neurosecretory granules are necessary to differentiate these tumors. One third of all Merkel cell carcinomas result in death. In the present paper, we present data on the clinical features, treatment and long-term follow-up of three patients.