Stage I AR-positive triple-negative invasive apocrine breast carcinoma: disease-free after surgery, radiotherapy and chemotherapy

What happened, in summary

A 58-year-old woman with no relevant family history had a left breast lump detected during routine health screening. Mammography showed a high-density spiculated lesion in the upper outer quadrant, categorized as BI-RADS 4c/5, and ultrasound showed a 1.0 x 1.1 cm spiculated hypoechoic lesion. FDG PET-CT showed mild uptake confined to the breast lesion and no FDG-avid axillary nodes or distant disease. Fine-needle aspiration was interpreted as infiltrating ductal carcinoma. She underwent left breast-conserving surgery with oncoplastic volume displacement and sentinel lymph node biopsy. Five sentinel nodes were removed and were negative, and final margins were negative. Final pathology showed a 1.7 x 1 x 1 cm invasive carcinoma with predominantly large eosinophilic cells and focal low-grade DCIS. The tumor was classified as carcinoma of no special type with apocrine differentiation, grade 2. Biomarker testing showed ER-negative, PR-negative, and HER2-negative disease, but androgen receptor staining was strong in 90% of tumor cells. Ki-67 was low at 8%. AE1/AE3 and CK7 were positive, TRPS1 was focally positive, and GATA3, DOG1, and SOX10 were negative. Adjuvant treatment included whole-breast radiotherapy, 40 Gy in 15 fractions over 3 weeks. She then received paclitaxel plus carboplatin every 3 weeks for 6 cycles, selected to balance triple-negative breast cancer treatment standards with the relatively indolent features of low-proliferative apocrine carcinoma. At 1 year, she remained disease-free with no clinical or radiologic recurrence. Her planned surveillance schedule was every 3 months for the first 2 years, every 6 months from years 2 to 5, and annually thereafter.