First, we evaluate whether tumor size, categorized as pT1a (0.1–0.5 cm), pT1b (> 0.5–1.0 cm), and pT1c (> 1.0–2.0 cm) according to the TNM classification of malignant tumors, UICC (TNM), is a good prognostic factor of survival in pT1N0 BRCA1/2-associated BC patients who did not receive chemotherapy. This evidence concerns the gene BRCA1 and breast cancer.