Salivary mucinous adenocarcinoma of the mandible.

Mucinous adenocarcinoma (MAC) is a malignancy rarely affecting the salivary glands, with fewer than 30 cases described in the medical literature. MAC is mostly observed in the minor salivary glands of the palate, and to date, no case of salivary MAC has been reported in the mandible. Identifying a salivary MAC may be both clinically and histopathologically challenging, as differential diagnosis must consider not only other salivary malignancies expressing a mucinous component but also metastases from MACs of the gastrointestinal tract, breast, and sweat glands that strongly resemble a salivary MAC on histopathology. We describe an 80-year-old man with a gingival overgrowth of the left mandible for the past 9 months, who was referred to our institution with an initial diagnosis of a periodontal reaction. On clinical examination, the mass mimicked a hyperplastic lesion; but after biopsy, the histopathologic pattern suggested a diagnosis of MAC. Herein, we present how comprehensive physical examination of the patient, immunohistochemistry study of the specimen, and radiological features helped in establishing the diagnosis of intraosseous salivary MAC, ruling out metastatic disease or other salivary neoplasms.