Merkel cell carcinoma with primary manifestation of the parotid gland.

Merkel cell carcinoma (MCC) is a rare, neuroendocrine carcinoma seen in fair-skinned people over age 65. Typically arising from Merkel cells of the skin, it may also develop in less common sites, including the parotid gland. MCCs are associated with ultraviolet light, impaired immune function, and Merkel cell polyomavirus. We describe a case of a 58-year-old Hispanic male, diagnosed with primary MCC of the parotid gland, with metastasis to the femur, without primary lesions of the skin. The patient presented after a 2-week duration of knee pain. A large neck mass was observed and explained to be rapid growing and painless. Upon palpation, the mass was firm, immobile, and 2cm in diameter. Exam findings were otherwise unremarkable. Laboratory studies showed normal calcium and alkaline phosphatase levels. Facial CT revealed two large necrotic masses in the left parotid gland. Fine needle aspiration of these masses confirmed Merkel Cell Carcinoma (MCC). Staging with CT imaging, revealed many necrotic lymph nodes. Evaluation for metastasis was warranted due to the knee pain, in which X-ray revealed lytic lesions throughout the femur. Confirmatory MRI showed an aggressive intramedullary lesion of the right distal femur. As per patient, the MCC parotid growth duration was less than 1 year, yet resulted in spread to lymph nodes, distal femur and knee, confirming the aggressive nature of the tumour. This case joins the few reported cases of parotid gland MCC, serving to educate that this elusive cancer may present anywhere and should be considered when evaluating all masses. [ABSTRACT FROM AUTHOR]