Localized male small-cell neuroendocrine breast cancer with complete response

What happened, in summary

This 47-year-old man from Syria noticed a suspicious lump in his left breast that had been present for about 2 months. On examination, the mass was solid, irregular, nontender, and measured about 1 x 1.5 cm in the upper outer breast. Ultrasound showed an 11 x 18 mm lesion suspicious for malignancy, along with a small axillary lymph node. CT did not show other lung, pancreatic, adrenal, or pelvic masses.

Core needle biopsy showed poorly differentiated small-cell neuroendocrine carcinoma of the breast, a rare form of breast cancer, especially in men. Immunohistochemistry supported the diagnosis, with synaptophysin positivity, weak cytokeratin positivity, HER2 negativity, and a Ki-67 proliferation index above 70%. Genetic testing was not performed. After multidisciplinary review, his disease was considered localized and potentially curable, with no clinical evidence of a primary tumor elsewhere.

He received 5 cycles of preoperative chemotherapy using a small-cell cancer regimen: cisplatin on day 1 plus etoposide for 3 days, repeated every 21 days. After 3 cycles, the tumor had shrunk to about 0.5 cm. Side effects included mild hair loss, nausea, and bone marrow suppression that improved with granulocyte-colony stimulating factor. He then underwent modified radical mastectomy with axillary lymph-node dissection. Pathology showed a complete response, and all 17 axillary lymph nodes were reactive rather than cancerous. The multidisciplinary team did not recommend postoperative breast radiation or prophylactic cranial irradiation. He entered surveillance rather than additional local therapy, and post-treatment CT showed no recurrence. After 18 months of follow-up, he remained disease-free.