Plasma cell mastitis (PCM) is a rare chronic inflammatory disease of the breast that mainly affects non-lactating women, with fewer than 100 cases reported in men worldwide. In men, it has nonspecific clinical and radiological features that often mimic breast cancer. The article describes a 55-year-old patient with a 6-month history of a left subareolar mass, initially diagnosed as malignancy on ultrasound (BI-RADS 4C) and mammography (BI-RADS 5). Despite a negative percutaneous biopsy and normal tumor markers, surgical excision was performed after multidisciplinary evaluation. Pathology confirmed PCM with dense plasma cell infiltration, multinucleated giant cells, and ductal ectasia. The patient achieved complete remission after margin-negative resection and at 12-month follow-up without recurrence. Obesity (BMI 31 kg/m²) and nipple inversion were identified as risk factors. Surgical excision is the gold standard for localized PCM, as nonsurgical treatments often lead to recurrence.