Examination of 6 T1a breast cancer cases treated at our hospital

T1a breast cancer with a tumor diameter of 5 mm is classified as microcarcinoma. In general, lymph node metastasis is rare, and the prognosis is relatively good, with a 5-year survival rate of ≥95%. Therefore, chemotherapy is not often used. However, depending on the histological type and other characteristics of the tumor, some patients show a rapid clinical course. Therefore, early detection of T1a breast cancer is also important. Under these circumstances, we decided to review cases of T1a breast cancer treated at our hospital. We retrospectively reviewed the data of T1a breast cancer patients who had undergone surgery at our hospital between April 2015 and March 2022. A total of 6 patients were included. The mean age was 65.8 ± 11.3 years, and all were women. Breast cancer was diagnosed by mammographic (MMG) screening in 4 of these patients and by palpation of a lump in the remaining 2 patients. The MMG findings were calcification in 3 cases and breast architectural distortion in 1 case. The subtype was luminal A in 2 cases, luminal B in 2 cases, human epidermal receptor 2 (HER2) in 1 case, and triple-negative (TN) in 1 case. The histological type was invasive ductal carcinoma (IDC) in 5 cases and invasive micropapillary carcinoma (IMPC) in 1 case. Of all the cases of T1a breast cancer treated at our hospital, we started treatment after the screening in 67%, suggesting that early detection and early treatment was possible in these patients. The cases included relatively highly malignant breast cancers, such as those with strong HER2 expression, TN, and IMPC. Many of the T1a breast cancer patients did not receive chemotherapy. Therefore, the detection of breast cancers measuring 5 mm in diameter by breast screening not only improves the cure rate of breast cancer, but is also of socioeconomic significance.