Primary Merkel Cell Carcinoma of the Submandibular Gland: When CK20 Status Complicates the Diagnosis.

Merkel cell carcinoma is a neuroendocrine tumor that occurs predominantly on the sun-exposed skin, with rare cases in the extracutaneous sites. It represents one of the extremely rare malignant neuroendocrine tumors of the salivary glands. We report a case of primary Merkel cell carcinoma of the right submandibular gland. The preoperative diagnosis was doubtful and the definitive histological diagnosis proved to be very difficult considering the extreme rarity of this tumor. The intraoperative evaluation of the macroscopic characteristics of the lesion led to an elective lymph node dissection. The extreme aggressiveness of the disease has resulted in the necessity of a new post-operative staging and in a multimodal treatment. This is the first primary submandibular gland Merkel cell carcinoma described in the literature. Differential diagnosis may be challenging and proper hematoxylin-eosin staining and immunohistochemical studies are mandatory.