Merkel cell carcinoma of the lower lip: A case report and literature review.

Merkel cell carcinoma (MCC) is an aggressive primary cutaneous neuroendocrine carcinoma that predominantly affects the sun-damaged skin of the head and neck region, extremities, and trunk of white older individuals. Microscopically, small to intermediate round blue cells show granular nuclei with a salt-and-pepper chromatin pattern, and are usually positive for epithelial and neuroendocrine markers, particularly for cytokeratin 20 in a perinuclear dot-like staining. The 5-year overall survival rate for individuals with localized MCC is 51% and the most common treatment choice is surgery with adjuvant radiotherapy. As far as we know, 23 cases of MCC of the lips have been reported to date in the English-language literature. We herein contribute by reporting a case of MCC affecting the lower lip of an 81-year-old male patient from Rio de Janeiro, Brazil, which likely represents the first reported case from Latin America. A review of the current literature is also included in an effort to familiarize providers with this rare, but potentially lethal neuroendocrine tumor.