Merkel cell carcinoma: differences between sun-exposed and non-sun-exposed variants--a clinical analysis of 36 cases.

Background: There are few studies focusing on the clinical characteristics of Merkel cell carcinoma (MCC).

Objective: To retrospectively analyze the clinical features of our patients and their relationship with sun exposure.

Methods: Thirty-six patients diagnosed with MCC (20 men and 16 women, mean age 72.08 years) were included in the study.

Results: 21 patients developed MCC in sun-exposed skin and 15 patients in non-sun-exposed areas. MCC was >2 cm in 19 cases. Six of the 7 patients who died as a result of MCC had non-sun-exposed tumors. Only tumor size >2 cm significantly influenced survival (p = 0.033).

Conclusion: Sun-exposed lesions tended to be <2 cm in diameter and were more common in men, while non-sun-exposed tumors were larger, usually occurring in women and carrying a greater likelihood of death by MCC. Non-sun-exposed tumors usually present as fast-growing, multilobar nodular lesions with a smooth shiny surface.