What happened, in summary

A 37-year-old woman noticed a painless lump in her left breast that grew over 6 months. Ultrasound showed a large cystic lesion, and mammography showed a high-density mass measuring about 9.9 cm, with mild axillary lymph-node enlargement. Chest CT ruled out lung metastases but confirmed axillary lymphadenopathy. Because the mass was large and growing, the team planned surgery. During the operation, a 2 cm axillary lymph node was removed first, and frozen section showed metastatic carcinoma. The surgeon then opened a 10 cm breast cyst containing pale yellow fluid; frozen section of the cyst wall also confirmed invasive carcinoma. Breast-conserving surgery was not suitable, so she underwent modified radical mastectomy with axillary lymph-node dissection. Final pathology showed grade III invasive carcinoma of no special type, with ductal carcinoma in situ making up 20% of the tumor. Seven of 15 axillary lymph nodes contained cancer, including 6 macrometastases and 1 micrometastasis, with extracapsular extension and vascular tumor emboli. Biomarker testing showed ER 50-60%, PR 20-50%, HER2 IHC 3+, Ki-67 40-50%, PD-L1 CPS 25, and low stromal TILs at 5%. Adjuvant therapy began on 17 December 2024 with TCbHP: docetaxel, carboplatin, pertuzumab, and trastuzumab, with 6 cycles planned. Maintenance trastuzumab plus pertuzumab was planned for 1 year afterward. She tolerated the first cycle well with supportive medications and continued regular monitoring between treatments. The pathology also showed vascular tumor emboli, extracapsular extension in involved nodes, weak androgen receptor staining, E-cadherin positivity, focal p63 positivity, and calponin negativity. These details supported an aggressive but treatment-directed HER2-positive, hormone receptor-positive breast cancer profile.