Ovarian cancer arising in endometrioid cysts: ultrasound findings

OBJECTIVES: To describe sonographic characteristics of malignant transformation in endometrioid cysts. METHODS: Women with a histological diagnosis of ovarian endometrioid cysts, borderline tumors arising in endometrioid cysts and carcinoma arising in endometrioid cysts, preoperatively examined sonographically, were included in this retrospective study. Gray-scale and Doppler ultrasound characteristics of the endometrioid cysts were compared with those of the borderline tumors and primary cancers arising in endometrioid cysts. The performance of an experienced examiner in classifying the masses was also assessed. RESULTS: Of 324 cases collected for the study, 309 (95.3%) lesions were classified as endometrioid cysts, four (1.2%) as borderline tumors arising in endometrioid cysts and 11 (3.4%) as carcinoma arising in endometrioid cysts. Women with malignant findings (borderline ovarian tumors and cancers) were older (median age 52 (range, 28-79) years) than those with benign endometrioid cysts (median age 34 (range, 18-76) years) (P<0.0001), and the prevalence of postmenopausal status was significantly higher in malignant cases. All (15/15) malignant tumors vs. 16% (50/309) of benign tumors were characterized by the presence of solid tissue (P<0.0001). The prevalence of solid tissue with positive Doppler signals was higher in malignant tumors (100%) than in benign cysts (7.8%) (P<0.0001). Papillary projections were a more frequent sonographic feature among malignant lesions (86.7%) than among benign endometrioid cysts (11.3%) (P<0.0001); power Doppler signals were detected within the projections in 92.3% and 37.1% of malignant and benign lesions, respectively. The examiner correctly diagnosed 94.8% (293/309) of benign lesions as benign and 93.3% (14/15) of malignant lesions as malignant. The risk estimation of the examiner was 'uncertain' in three (20%) and 'probably/certainly malignant' in 12 (80%) of 15 malignant cases. CONCLUSION: Borderline tumors and carcinomas arising in endometrioid cysts show a vascularized solid component at ultrasound examination.