Bilateral salpingo-oophorectomy (BSO) is increasingly employed as a risk-reducing strategy for epithelial ovarian cancer (EOC). We report the third case of a patient developing primary peritoneal cancer two decades after a bilateral salpingo-oophorectomy. This 66-year-old female underwent a hysterectomy for pelvic pain at age 28 and a subsequent bilateral salpingo-oophorectomy (BSO) at age of 45 for a pelvic mass. Presenting with a 6-month history of increasing abdominal girth, decreased energy, and a reduction in appetite, she was consented for a unilateral salpingo-oophorectomy, omentectomy, and cytoreductive surgery. Pathology specimens revealed a high grade metastatic papillary serous carcinoma consistent with a primary gynecologic origin. It is unlikely that an occult malignancy was missed at the time of pathologic assessment following her previous BSO; therefore it provides evidence that primary peritoneal cancers can arise through the malignant transformation of benign endosalpingiosis.