Merkel cell carcinoma: a clinicopathological study of 11 cases.

Objective: To report our 12-year experience with Merkel cell carcinomas (MCCs) from a clinical and pathological point of view.

Subjects And Setting: Eleven MCCs were diagnosed at our institution between 1991 and 2002.

Methods: A retrospective clinical, histopathological and immunohistochemical study was performed. Age, gender, location, size, stage, treatment and follow-up data were collected. Histopathological pattern and immunohistochemical study with CAM 5.2, cytokeratin 20 (CK20), CK7, Ber EP4, neurofilaments, synaptophysin, chromogranin, S100 protein, p53 protein, CD117, leucocyte common antigen (LCA) and Ki-67 were accomplished.

Results: Six females and five males with a mean age of 82 years were identified. Tumours were located on the face (n = 6), extremities (n = 3) and trunk (n = 1). At diagnosis, one patient was in stage Ia, six in stage Ib, three in stage II and one in stage III. All but one patient experienced wide surgical excision of the tumour. Additional treatment consisted of lymph node dissection in two patients, radiotherapy in four patients and systemic chemotherapy in one patient. Local recurrence developed in five patients. Three patients died because of MCC after 14 months of follow-up. Intermediate-size round cell proliferation was found in all cases. Additional small-size cell pattern and trabecular pattern were observed in seven and six cases, respectively. Eccrine and squamous cell differentiation were found in three cases. A dot-like paranuclear pattern was observed in all cases with CAM 5.2 and neurofilaments, and in 89% of cases with CK20. Seventy-five per cent of cases reacted with Ber EP4, chromogranin and synaptophysin, 70% with p53, 22% with S100 protein, 55% with CD117 and none with LCA. Ki-67 was found in 75% of tumoral cells on average. Fifty per cent of MCCs reacted with CK7 and showed eccrine differentiation areas.

Conclusions: MCC is an aggressive neuroendocrine tumour of the elderly. Wide surgical excision is the recommended treatment. Lymph node dissection, adjuvant radiotherapy and chemotherapy decrease regional recurrences but have not been demonstrated to increase survival. Immunohistochemically, MCC is an epithelial tumour with neuroendocrine features.