Merkel Cell Carcinoma Arising in Combination With Basal Cell Carcinoma: A Rare Diagnosis and Potential Pitfall

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine skin cancer, often associated with a poor prognosis due to its propensity for rapid growth, local recurrence, and metastasis. Combined squamous and Merkel cell carcinoma are welldescribed in the literature; however, concomitant basal cell and Merkel cell carcinoma are exceedingly uncommon. We report a 69-year-old male patient presenting with red, crusted, exophytic plaque on the right postauricular area. Further evaluation revealed nodular basal cell carcinoma (BCC) with an additional, morphologically, and immunophenotypically distinct neuroendocrine component, and areas indicating possible lymphovascular invasion. Overall, the histopathology was most compatible with a combined tumor involving Merkel cell carcinoma and basal cell carcinoma. Our case suggests that this unusual morphologic appearance of Merkel cell carcinoma can be overlooked and should be recognized when evaluating biopsies demonstrating basal cell carcinoma.