Odds of Merkel cell carcinoma metastases associated with primary anatomic site and laterality

Merkel cell carcinoma (MCC) is a neuroendocrine skin malignancy associated with ultraviolet radiation exposure and the Merkel cell polyomavirus. This study aims to examine associations between primary tumor anatomic site, laterality, and metastases in MCC in the Surveillance Epidemiology and End Results (SEER) database and an academic center MCC database in Rhode Island (RI). A retrospective chart review of 92 MCC cases from RI Hospital and 2845 subjects from the SEER registry was analyzed. Logistic regressions in each cohort were performed to calculate odds ratios (OR), adjusting for sex, age at diagnosis, race, and marital status. The majority of tumors were left-sided in the SEER cohort (53.0%) and RI cohort (56.5%), and located on the head and neck region in the RI cohort (60.9%) and the trunk and extremities in the SEER cohort (70.8%). Left-sided tumors compared to right-sided tumors were marginally associated with increased odds of metastasis in the SEER cohort (OR 1.05, 95% CI 0.87, 1.27); however, decreased risk of MCC was found in the RI cohort (OR 0.33, 95% CI 0.13, 0.80). Tumors located on the trunk and extremities were marginally associated with decreased odds of metastasis compared to head and neck tumors in both databases (SEER: OR 0.88, 95% CI 0.72, 1.08 and RI cohort: OR 0.62, 95% CI 0.25, 1.50). Left-sided tumors located on head and neck showed a suggestive evidence of increased odds of MCC among females in the SEER data (OR 1.77, 95% CI 0.98, 3.23). Our study potentially has important implications for clinical tumor diagnosis and prognostication as well as improved understanding about the epidemiology of MCC.