Male breast cancer (MBC) is a rare disease that occurs in ~0.2% of all neoplasms among men. The risk of developing MBC is higher in men with a genetic mutation (7%). The aim of this study was to evaluate the association between c.2808_2811del ACAA (p.Ala938Profs) mutation in MBC and clinicopathological factors. A 75-year-old patient was admitted to the Genetic Outpatient Clinic with a diagnosis of right breast cancer and with a family history of cancer (two daughters who were diagnosed with breast cancer at ages 46 and 38 years). Postoperative histopathological examination revealed tumor type pT2 N1a Mx, NST NG-3 G-3, Ki-67 (75%), HER2 (+), ER (+++), PR (+++), invasive carcinoma and luminal B subtype. The complete coding sequences of the and genes were analyzed for genomic DNA material using next generation sequencing on the Ion Torrent platform. The c.2808_2811delACAA (p.Ala938Profs) mutation was observed in the gene. The presence of the c.2808_2811delACAA (p.Ala938Profs) mutation in the gene was confirmed using the Sanger method. The same gene mutation was reported in one of the patient's daughters. The detected mutation causes the frameshift mutation, resulting in the creation of an additional translation termination codon and the synthesis of an abnormal protein. This mutation was associated with a later age of disease, a higher histological degree, a higher mitotic index, a positive steroid receptor status and the luminal B subtype HER2- breast cancer.