Track: Clinical Studies

Abstract:

BACKGROUD: Merkel cell carcinoma (MCC) is a rare, aggressive, and highly metastatic neuroendocrine tumor, potentially associated with Merkel cell polyomavirus (MCPyV), particularly in non-sun-damaged areas. This study analyzes a cohort of MCC cases, focusing on clinicopathologic features, including MCPyV status and gender-based differences.

DESIGN: A retrospective-cohort study of MCC cases diagnosed from December 2011 to March 2025, assessing: 1) Demographics (age, gender); 2) clinical profile (follow-up, treatment, metastasis, and MCPyV status); 3) sun-damaged areas (categorized as non-, low-, or chronically-sun-damaged areas); 4) histological grade; and 5) IHC marker expression. Statistical analysis used 95% CI with significance at p<0.05.

RESULTS: Among 170 cases, 59 were female (34.7%) and 111 male (65.3%) (p=0.0055). Mean age was 72 years, and mean follow-up was 2.8 years (p=0.97 and 0.99, respectively) for both genders. For women and men, respectively: Chemotherapy use, 64% and 52%); radiotherapy use: 77% and 74%; sentinel node metastasis: 89% for both; distant metastasis: 43% and 45.5%; sun-damaged areas (non-/low-/chronically-): 29%/39%/34% and 36%/26%/34%; survival with positive MCPyV: 71% and 59%; and high-grade histology: 81% and 94% (p>0.05 for all). MCPyV positivity was 68% in females, 52% in males (p=0.012), mainly in high chronically-sun-damaged areas, 92% vs. 52% (p=0.014). General IHC positivity: Synaptophysin 98.4%, neurofilament 91.7%, chromogranin 89.1%, and CK20 85.3% (p<0.0001).

CONCLUSION: MCC was more frequent in men, but MCPyV was significantly more frequent in women, especially in chronically-sun-damaged areas, challenging original assumptions, but aligned with recent studies pointing. MCPyV-positive tumors were strongly associated with classic neuroendocrine IHC markers.

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Jorge Torres-Mora