Prognostic Factors in Merkel Cell Carcinoma: A Retrospective Single-Center Study in 90 Patients.

Merkel Cell Carcinoma (MCC) is a rare but highly aggressive neuroendocrine neoplasm of the skin. This study aimed at describing characteristics, treatment, and prognosis of a series of consecutive cases of MCC patients, in order to contribute to the investigation of this rare malignancy and provide better patient care. This is a retrospective cohort study including all 90 patients diagnosed and/or treated for MCC between 1991 and 2018 at the Veneto Institute of Oncology in Padua (Italy). Patient and tumor characteristics, treatment, and immunohistochemical data were extracted from a prospectively collected local database. There were 68 primary (76%) and 22 non-primary (15 occult primary, three metastatic, four recurrence) tumors (24%). CK20 expression was associated with reduced overall (HR 2.92, 95% CI 1.04⁻8.16) and disease-specific (HR 4.62, 95% CI 1.31⁻16.28) survival. Immunomodulatory regimens for treatment of other comorbidities were associated with reduced disease-specific ((HR 2.15, 95% CI 1.06⁻4.36) and recurrence-free (HR 3.08, 95% CI 1.44⁻6.57) survival. Iatrogenic immunomodulation resulted as the main factor associated with impaired prognosis. Lack of CK20 expression was associated with better survival.