We present the case of a 67-year-old patient with a BRCA1 mutation and breast cancer who underwent prophylactic oophorectomy. After 6 years, an abdominal computed tomography revealed a pelvic mass which proved to be a poorly differentiated serous carcinoma originating from the right residual tube which previously had not been removed during prophylactic surgery. This case report suggests that much effort should be made during prophylactic oophorectomy to completely remove the tubes, especially in light of the recent pathologic theories on the tubal origin of ovarian cancer.