The aim of this study was to report a case of malignant transformation from residual endometriosis following hysterectomy and bilateral salpingo-oophorectomy in a female patient with a positive family history of ovarian and colon cancer resulting from residual endometriosis. A 42-year-old female patient from a family with hereditary non-polyposis colorectal cancer (HNPCC) diagnosed with bilateral ovarian endometriosis underwent a hysterectomy and bilateral salpingo-oophorectomy. Two years later, the patient was diagnosed with malignant ovarian cancer. Histological examination revealed an endometrioid adenocarcinoma with transitions between endometriosis and adenocarcinoma. The patient was diagnosed with ovarian endometrioid carcinoma, at FIGO stage IIC. In future, the family history of female patients with endometriosis should be collected. The association between the malignant transformation of endometriosis and HNPCC should be studied further in a research setting.
Keywords: hereditary non-polyposis colorectal cancer; malignant transformation; residual endometriosis.