Merkel Cell Carcinoma (MCC) is a rare, aggressive, cutaneous cancer that typically occurs in sun-exposed areas of elderly, Caucasian, immunocompromised patients. Polyomavirus (MCPyV) infection and ultraviolet radiation have a significant relation to MCC pathogenesis. Only limited cases were reported about MCC occurring on sites that are not sun-exposed in Asian patients, as it is extremely uncommon. In this report, we describe a case of a 79-year-old Saudi male who presented with multiple fleshy nodules on his right leg, which coalesce together, forming a large fungating mass. Upon histological and immunohistochemical analysis, tumor cells were positive for Synaptophysin and CK20 (dot like paranuclear pattern). However, they were negative for CD45, CD20, and CD3. Tumor features confirmed the diagnosis of MCC, and the patient was referred to the oncology department for further management. Due to its low incidence rate and lack of characteristic clinical manifestations, the final diagnosis of MCC relies on the analysis of histological findings and immunohistochemical markers obtained after lesion biopsy or resection. The primary goal of sharing this case is to bring MCC, a diagnostic challenge, to the attention of dermatologists and oncologists since early detection and timely treatment are crucial.

Osama Alsharif attained board certifications in dermatology from Saudi Arabia, Jordan, and the Arab Board. He successfully completed clinical fellowships in Pediatric Dermatology at the University of Miami Hospital (USA) and Great Ormond Street Hospital (UK). With over 15 years of experience, he has contributed to the field of dermatology through multiple publications. Dr. Alsharif remains committed to staying abreast of the latest advancements in his field by actively participating in conferences and workshops.