Case Report: Mucoepidermoid carcinoma in rare locations: a report of two cases.

Mucoepidermoid carcinoma (MEC) is a common malignancy of the salivary glands, accounting for 10-15% of salivary gland tumors. It mostly occurs in the salivary glands and very rarely in the lungs and mammary glands. The incidence of breast MEC is only 0.2% to 0.3% of all primary breast tumors. Pulmonary MEC accounts for only 0.1-0.2% of all lung tumors. This report presents two cases of MEC occurring in rare locations: the left lower lung and the breast. Both cases presented different clinical features and histopathological characteristics. The immunohistochemical analysis of Ki-67, CK5/6, P63 and other positive results also confirmed the diagnosis. Surgical resection was the primary treatment in both cases, with the patient with lung involvement additionally receiving chemotherapy and radiotherapy. These cases underscore the importance of recognizing MEC in atypical locations, as timely diagnosis and proper treatment approaches are vital for improving patient outcomes. From these cases, the complexity of MEC is highlighted and the necessity of precise histopathological diagnosis, especially in rare sites, is emphasized.