Synchronous Diagnosis of Ductal Carcinoma In Situ and Mucoepidermoid Carcinoma of the Parotid Gland: A Rare Case of Dual Primary Malignancy.

The coexistence of two histologically and anatomically distinct malignancies, ductal carcinoma in situ (DCIS) and mucoepidermoid carcinoma (MEC), in the same patient is a clinically rare phenomenon. MECs of the salivary glands, most often arising in the parotid, can display a range of histological grades and clinical courses. We report the case of a 76-year-old woman with a prior diagnosis of hormone receptor-positive DCIS who developed low-grade MEC of the parotid gland nearly a decade later. Possible etiologic factors discussed include coincidental tumor development, prior treatment effects, inherited predisposition, and hormonal influences. A focused literature-based discussion supports the analysis of this unique case.