Fig. 1

Images and findings of reported case of malignant transformation. a The sizes of the left and right cysts were 7 cm and 3 cm in diameter, respectively, and the cysts were diagnosed by transvaginal ultrasound examination 1 day before surgery. b Intraoperative image of the left ovarian endometrioma (OMA). The ovarian cyst contains chocolate-like fluid. c Gross appearance of the left ovary at laparoscopic cystectomy (LC). The ovarian cyst does not contain a solid component. d Pathological findings of the left OMA (H&E staining, conventional light microscopy at a magnification of ×20). Abundant hemosiderin-laden macrophages were present in the cyst wall, as indicated by arrows. e T2-weighted magnetic resonance image at diagnosis of malignant transformation. There was a cystic left ovarian mass (7 cm in diameter) with a solid component (arrow). One scale = 1 cm. We could not obtain a magnetic resonance image before LC, because the patient had undergone a magnetic resonance imaging examination before visiting our hospital. f Gross appearance of left ovarian carcinoma and other organs removed at surgery for ovarian cancer. The ovarian cyst contains a large solid component with chocolate-like fluid. g, h Pathological findings of the left ovarian clear cell carcinoma, as indicated by a circle (H&E stain, original magnification in g ×20 and h ×200). Tumor cells have eosinophilic cytoplasm and hyalinized stroma