Male invasive breast carcinoma containing both mucinous and micropapillary components with axillary lymph node metastasis: a rare case report with literature review.

[BACKGROUND] Male breast cancer (MBC) accounts for less than 1% of all breast cancer cases. Due to societal cognitive biases, males' neglect of breast health, and associated stigma, diagnosis is often delayed, leading to disease progression. Current diagnostic and therapeutic protocols for MBC are mostly derived from female breast cancer (FBC), but gender-specific differences in anatomy, hormonal milieu, and tumor biology limit their applicability. This case is unique for the rare coexistence of mucinous and micropapillary components within a single MBC tumor, compounded by a 1-year diagnostic delay largely due to patient stigma.

[CASE DESCRIPTION] A 47-year-old male incidentally discovered a painless soybean-sized mass near his right nipple one year prior to admission. Owing to insufficient awareness and stigma, he did not seek timely medical attention, and the mass gradually enlarged. He was diagnosed with a breast mass and axillary lymphadenopathy at a local hospital and referred to our institution, where biopsy confirmed invasive breast cancer. After being persuaded by our doctor, he finally decided to put aside his shame and receive treatment. Modified radical mastectomy of the right breast was performed. Pathological examination revealed grade III invasive carcinoma of no special type with mucinous and micropapillary components, measuring 18 mm × 15 mm × 15 mm, with 2/17 axillary lymph node metastases and pathological staging pT1N1Mx. Immunohistochemistry showed estrogen receptor (ER) (70%, 2+), progesterone receptor (PR) (80%, 3+), and no HER2 amplification. Postoperatively, the patient received 4 cycles of docetaxel and epirubicin (TE) chemotherapy and is currently taking tamoxifen with no recurrence or metastasis during follow-up.

[CONCLUSIONS] This case highlights the importance of early detection and treatment of breast abnormalities in men. Its rare mixed histological phenotype enriches MBC case literature and provides a reference for the diagnosis and treatment of special subtypes. It also calls for enhanced public education on male breast health, development of gender-specific precise diagnostic and therapeutic strategies, and clinicians' attention to patients' stigma with targeted psychological counseling to reduce diagnostic delays.