Characteristics of Spontaneous Regression in Merkel Cell Carcinoma: A Retrospective Analysis of Patient and Tumor Features.

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine neoplasia. MCC complete spontaneous regression (CRS) has been linked to good prognosis. We conducted a retrospective review of a single-center cohort of MCC patients to analyze the characteristics of patients and tumors that exhibited regression. The calculated incidence of regressión was 4.5% (5/112). Median age at diagnosis was 69 years (RIQ 31), tumors were primarily located on the head and neck and patients had low rates of immunosuppression. After a median following-up of 4 years none of the patients showed recurrence or distant metastases. Merkel cell polyomavirus (MCPyV) positivity was associated with regression (P=0.045). Despite limited understanding of regression mechanisms, biopsy-induced immune responses linked with host and tumor factors such as age,immunosuppression or MCPyV positivity may play an important role. More research in this field is crucial for the comprehension of this rare phenomenon.