Occult Male Breast Cancer Presenting as Axillary Lymphadenopathy: A Rare Case Report

Background Male breast cancer (MBC) is a rare condition within the broader spectrum of breast cancer. It is most commonly diagnosed in men between the ages of 60 and 70, with an average age of 67 at diagnosis ^[1] . MBC accounts for less than 1% of all breast cancer cases, with incidence varying across ethnic groups. Rates are highest among non-Hispanic Black men (1.89 per 100,000) ^[3] . Elevated incidence in South and Central Africa may be linked to hyperestrogenism from liver infections ^[4] . Genetic predispositions, especially BRCA2 mutations, significantly increase the risk of MBC greater than BRCA1 mutations. The most frequent histological type is infiltrating ductal carcinoma, while invasive lobular carcinoma is exceptionally uncommon. MBC tumours are typically hormone receptor positive [5]. Key risk factors for MBC include older age, Black ethnicity, genetic mutations, family history, liver cirrhosis, and testicular disorders. Most patients present with painless breast lumps, and about 50% have lymph node involvement at diagnosis ^[1] . Case presentation A 61-year-old male presented with a 6-year history of progressive, non-tender swelling in the left axilla, with no associated systemic symptoms. Clinical examination revealed matted, erythematous lymph nodes, prompting FNAC and subsequent excision biopsy. Cytology demonstrated markedly atypical tumour cells with high N:C ratio and significant pleomorphism. Histopathology of the lymph node confirmed effaced architecture with malignant cells arranged in sheets, cords, and globular patterns, along with capsular invasion. Immunohistochemistry showed CK7 and GATA3 positivity and strong HER2 (3+) expression, while ER, PR, mammaglobin, and CK20 were negative—findings consistent with metastatic HER2-positive primary breast carcinoma. PET imaging revealed metabolically active axillary and deep pectoral nodes. The patient received neoadjuvant chemotherapy with docetaxel, carboplatin, trastuzumab, and filgrastim, followed by modified radical mastectomy. While the breast parenchyma showed complete pathological response, residual nodal disease persisted. Conclusion This case highlights the diagnostic challenge of male breast cancer (MBC), particularly when presenting solely as axillary lymphadenopathy. Immunohistochemistry and PET imaging played essential roles in establishing diagnosis and staging. Timely neoadjuvant chemotherapy and surgery achieved primary tumour clearance, underscoring the importance of early suspicion, comprehensive evaluation, and guideline-based management of HER2-positive MBC.