Breast Carcinomas Resembling Acinic Cell Carcinoma: Comprehensive Analysis of 14 Cases and Review of the Literature.

Acinic cell carcinoma (AciCC) of the breast is an exceptionally rare subtype of invasive breast carcinoma, often exhibiting a triple-negative phenotype and relatively indolent behavior. Since the first case reported by Roncaroli and colleagues in 1996, no more than 60 additional cases have been described in English medical journals, usually as case reports or small case series. In this study, we presented an in-depth analysis of 14 cases of AciCC of the breast, including 4 pure AciCCs and 10 AciCCs mixed with other histologic types. We reported the clinicopathologic characteristics, histologic components, treatment modalities including response to neoadjuvant treatment in 3 patients, and outcomes. In addition, we assessed the expression of nuclear transcription factor nuclear receptor subfamily 4 group A member 3 by immunohistochemistry and gene rearrangements by fluorescence in situ hybridization, which has been implicated in AciCC of the salivary gland. All 14 cases were negative for nuclear receptor subfamily 4 group A member 3 expression, and no gene rearrangements were detected. We also conducted a thorough review of the literature to highlight advancements in understanding this rare breast cancer subtype. This study aims to enhance clinical knowledge of AciCC of the breast and contributed to growing evidence that AciCC of the breast and AciCC of the salivary glands appear to be unrelated entities, despite sharing a similar histologic appearance.