Acinar Salivary Gland Choristoma in the Mammary Gland in a Patient with Gynecomastia: A Rare Finding, Diagnostic Considerations, and Review of Published Evidence.

To report a case of salivary gland choristoma in a patient with gynecomastia. While it is commonly found in the head and neck region, its occurrence in the breast is exceedingly rare. We report a unique case in which a salivary gland acinar choristoma was incidentally identified in a 43-year-old man who underwent surgery for gynecomastia. Histological examination revealed typical features of gynecomastia along with a well-circumscribed area composed exclusively of salivary acini, with no ductal structures and no continuity with adjacent breast epithelium. Immunohistochemical staining confirmed acinar differentiation with positivity for α-amylase, S100, SOX10, and DOG1 expression. The absence of epithelial continuity supports a choristomatous rather than a metaplastic origin. Only two cases of salivary gland choristoma in breast tissue have been reported in the literature. These findings underscore the potential plasticity of mammary cells and the importance of considering salivary gland choristoma in the differential diagnosis of unusual breast lesions. Accurate diagnosis requires careful histopathological and immunohistochemical evaluation to differentiate these lesions from neoplastic processes with similar morphology.