Merkel cell tumor of the eyelid. A clinicopathologic case report.

We treated a patient who had clinical and pathological findings of a primary cutaneous tumor of the eyelid with histological and ultrastructural features of a Merkel cell carcinoma. This neoplasm is composed of cells that are thought to be derived from the neural crest and are found normally in the skin. While it may be a low-grade malignant neoplasm, this tumor can grow rapidly and metastasize. Histologically, it can mimic a metastatic undifferentiated small-cell carcinoma from the lung or other primary sites. To our knowledge, this is the first reported case involving an eyelid.