A rare ER-positive secretory breast carcinoma: diagnostic challenges and surgical treatment

Secretory breast carcinoma (SBC) is a rare, slow-growing type of breast cancer with a good prognosis, accounting for less than 1% of all breast cancers. It is associated with the ETV6-NTRK3 gene translocation and has a triple-negative molecular profile, but unlike most triple-negative breast cancers, it is less aggressive and rarely metastasizes.

A 47-year-old woman presented with bloody breast discharge and a lump. Sonomammography revealed BIRADS-4 (Breast Imaging-Reporting and Data System) cystic lesions. Biopsy confirmed low-grade secretory carcinoma, estrogen receptor (ER)-positive, progesterone receptor (PR)- and Human Epidermal growth factor Receptor 2 (HER2)-negative. After a modified radical mastectomy with lymph node dissection, histopathology showed clear margins and no lymph node involvement. At her 1-month follow-up, she had no complications and full shoulder mobility.

SBC is a rare, low-grade breast cancer, more common in young individuals but occurring across all ages. It presents as a painless mass, often mistaken for a fibroadenoma. Histologically, it shows microcystic and tubular features with Periodic acid-Schiff positive material. SBC is usually triple-negative (ER, PR, and HER2), but ER positivity has been reported. Treatment primarily involves surgical excision, with the role of axillary node dissection debated due to low metastatic risk. Tropomyosin receptor kinase (TRK) inhibitors are being explored for NTRK fusion cancers like SBC.

SBC diagnosis requires confirmation of the ETV6-NTRK translocation. Though typically triple-negative, hormone expression varies. Treatment involves mastectomy, with lymph node dissection debated due to low metastasis risk. Evidence for adjuvant chemotherapy is limited in SBC management.