Track: Case Reports

Abstract:

While the main risk factors for cutaneous squamous cell carcinoma (SCC) and Merkel cell carcinoma (MCC) are similar (including sun exposure and weakened immunity), these tumors are only rarely seen as a combined carcinoma. Four cases of combined SCC/MCC from 1/2024 to present were reviewed to highlight the diagnostic and clinical implications of this rare neoplasm. The patients ranged in age from 34 to 85 years old and included three men and one woman. The primary lesions were present on the forearm, neck, back and chest, and all were diagnosed with immunohistochemical stains including CK20 and neuroendocrine markers. Metastatic MCC developed in 75% of the patients, including two with metastases to regional lymph nodes and one with systemic metastases. After radiation and/or chemotherapy in the patients with metastases, two are alive with no evidence of disease while one is alive with disease progression. In summary, our patients with combined SCC/MCC had a higher likelihood of having both local and distant metastases than that generally expected from SCC alone, and the metastatic component was MCC in all three cases, with subsequent widespread therapy-resistant disease in 25% of the patients. This highlights the importance of diagnosis of the Merkel cell component, which can be overshadowed by the SCC component and missed with dire clinical implications. Future studies are needed to explore pathogenic links, such as immunosuppression or viral associations, and optimize diagnostic and treatment strategies.

William O' Connor

Affiliation

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(311) Combined Squamous Cell Carcinoma and Merkel Cell Carcinoma: Diagnostic and Clinical Implications in Four Cases