Stage IIB HER2-positive apocrine breast carcinoma treated with chemotherapy, trastuzumab, radiation, and tamoxifen

What happened, in summary

A 37-year-old woman found a nodule in the lower part of her right breast during self-examination. The lump had been present for about 11 months and was not associated with breast pain or nipple discharge. During pre-treatment assessment, she was also incidentally diagnosed with HIV infection. Examination found a firm, mobile, non-tender 2 cm breast nodule and no palpable axillary lymph nodes. Mammography showed 2 highly suspicious masses with microcalcifications, categorized as BI-RADS 4C. Core biopsy showed a poorly differentiated carcinoma, initially raising the possibility of lobular carcinoma or invasive ductal carcinoma of no special type. Staging CT did not show distant disease. She underwent right radical mastectomy with axillary lymph node dissection. The surgical specimen contained 2 poorly circumscribed tumors, one measuring 3 x 1.5 x 1 cm and the other 3 x 2 x 1.5 cm. Final pathology showed both tumors had identical apocrine carcinoma morphology, with negative margins, no vascular emboli, no Paget disease, and no subareolar duct involvement. Three of 20 lymph nodes contained metastases. The cancer was staged pT2N1cM0, consistent with Stage IIB disease. Biomarker testing showed ER positivity in 80% of cells, PR positivity in 5%, HER2 overexpression confirmed by HercepTest and FISH, and Ki-67 of 15%; AR testing was not performed. After surgery, she received 4 cycles of anthracycline-cyclophosphamide chemotherapy, followed by 3 cycles of paclitaxel with trastuzumab. Trastuzumab continued as maintenance therapy. She then received adjuvant radiation to the right supraclavicular region and chest wall, 42 Gy in 15 fractions, followed by tamoxifen 20 mg daily for 5 years. At 7 months, she remained in remission without local recurrence or distant metastasis.