A case of triple-negative breast cancer diagnosed by MRI-guided biopsy during surveillance of unaffected BRCA1 pathological variant carrier

We report a case of triple-negative breast cancer (TNBC) based on MRI-guided biopsy during surveillance of an unaffected BRCA1 pathological variant. The patient was a 37-year-old woman who was found to be BRCA1-positive following the diagnosis of a relative at the age of 29, and breast surveillance including MRI was conducted thereafter. Seven years later, an irregular mass of 9mm in the left C region appeared on breast MRI, and the diagnosis of breast cancer was made by MRI-guided biopsy. Left mastectomy + sentinel lymph node biopsy and right risk-reducing mastectomy were performed. The left side showed no residual lesion after biopsy, only DCIS, and the right side showed no evidence of malignancy. She is now under observation without adjuvant chemotherapy. It is considered that chemotherapy could have been avoided due to the detection of early breast cancer by appropriate surveillance. Diagnosis, surveillance, and risk-reducing surgery for blood relatives of BRCA-positive breast cancer patients are not covered by insurance, and the establishment of such a system is a future challenge. (author)