BREAST NODULE AFTER PROPHYLACTIC MASTECTOMY. K. Ghosh 1 , K.R. Brandt 1 ; 1 Mayo Clinic, Rochester, MN (Tracking ID #75726) LEARNING OBJECTIVES: 1. Build awareness among physicians that prophylactic mastectomy does not completely eradicate the possibility of breast cancer. 2. Emphasize that any breast lump after prophylactic mastectomy warrants complete work-up to rule out breast cancer. CASE INFORMATION: A 56 year-old lady with fibrocystic changes in the breast had undergone several benign right breast biopsies for mammographically detected abnormalities, and finally decided to have bilateral prophylactic mastectomy to prevent the anxiety associated with these biopsies. Following the mastectomies, she had bilateral pedicle transverse-rectusabdominis-myocutaneous (TRAM) flap reconstruction of the breasts with a smooth postoperative recovery. She was very satisfied with the outcome of the procedure. Four months after the surgery, the patient incidentally felt a lump in the left upper breast and when it persisted for about a month, the patient sought further evaluation. Examination revealed a firm, non-tender, fixed mass with ill-defined margins in the left upper breast. Ultrasound evaluation of the palpable mass revealed a heterogenic echotexture with no evidence of malignancy. Diagnostic left mammogram revealed no evidence of malignancy. Magnetic resonance imaging of the breast with dynamic gadolinium enhancement was then recommended and showed benign appearing localized collection of fat lobules and postoperative changes. The patient continues to do well on follow-up. IMPLICATIONS/DISCUSSION: The management of women at high-risk of breast cancer includes the options of surveillance, chemoprevention, prophylactic mastectomy and/or prophylactic oophorectomy. Prophylactic mastectomy is an option for risk reduction of breast cancer, and in women with a strong family history, has been associated with a 90% relative risk reduction. The procedure does not however, eradicate the risk of breast cancer as residual breast tissue may be left behind depending on the surgical technique. Therefore, any breast lump after PM must be evaluated to rule out breast cancer. In general, breast lumps after PM are often benign and related to fat necrosis as was the case in our patient, but the possibility of malignancy must be borne in mind when evaluating these patients.