[A Case of T1a Breast Cancer with Axillary Lymph Node Metastasis].

A breast cancer with tumors smaller than or equal to 5mm in diameter is treated as a microscopic lesion and axially lymph node metastasis is considered to be rare. A 52-year-old female was found to have an abnormal shadow on mammography. An ultrasonography revealed a poorly defined and irregular shaped mass with calcification, 4mm in diameter, in the AC area of her left breast. We performed vacuum-assisted biopsy and diagnosed with invasive ductal carcinoma. Under a preoperative diagnosis of left breast cancer with cT1aN0M0, stage I , Luminal A like, we underwent partial mastectomy with sentinel lymph node biopsy. The intraoperative consultation suggested sentinel lymph node metastasis and we therefore performed level II axillary lymph node dissection. The size of the tumor was 4mm and diagnosed with pT1a breast cancer. Histopathological diagnosis was papillotubular carcinoma. Radiotherapy was performed(total: 50 Gy)followed by endocrine therapy (tamoxifen). She is alive without recurrence and metastasis 5 years after surgery.