Male metaplastic breast cancer with poor prognosis: A case report

BACKGROUND: Metaplastic breast cancer (MBC) is a rare subtype of breast cancer. They constitute less than 1% of breast cancer cases and are much rarer in males. There are few reports of MBC because of its rarity. MBC, an aggressive type of cancer, is refractory to common treatment modalities of breast cancer and has a poor prognosis. CASE SUMMARY: We report a case of MBC in a 78-year-old man. He visited our clinic with a palpable mass on the left breast with no masses in the axillary areas. He had previously undergone robot-assisted laparoscopic radical prostatectomy for prostate cancer, but there was no family history of malignancy. The breast mass was visible on ultrasonography, mammography, and magnetic resonance imaging, and chest computed tomography revealed a lung mass in the posterior basal segment of the right lower lobe. The patient was diagnosed with metaplastic carcinoma on core needle biopsy with lung metastasis. Total mastectomy with sentinel lymph node biopsy and video-assisted segmentectomy of the right lung was performed. However, multiple metastases appeared 3 mo after surgery in the brain, chest, and abdomen, and the patient died 5 mo after the initial diagnosis. CONCLUSION: MBC is an aggressive and extremely rare breast cancer type. Further case reports are needed to determine the optimal treatment.