Bona fide primary Merkel cell carcinoma of an intraparotid lymph node in a HIV-positive patient.

Merkel cell carcinomas are uncommon malignant tumors thought to originate from the neuroendocrine cells of the skin that mainly affects sun-exposed body areas, particularly the head and neck. In approximately 10% of cases, they present with localized lymphadenopathy without any clinical evidence or history of a primary lesion, but a truly primary lymph node Merkel cell carcinoma may occur, possibly originating from epithelial inclusions or an anomalous neuroendocrine differentiation of hematopoietic stem cells. It has been observed that Merkel cell carcinoma is more likely to affect patients whose immune status is impaired as a result of iatrogenic immunosuppression, human immunodeficiency virus infection, or hematological malignancies. This study reports the case of a bona fide primary Merkel cell carcinoma arising in an intraparotid lymph node of a patient infected by HIV that had a particularly unfavorable clinical course.