Abstract
Diaphragmatic endometriosis is extremely rare. Although endometriosis is considered generally benign, malignant transformation of endometriosis was reported in 1925. Multiple studies have since described clear cell carcinoma (CCC) or endometrioid carcinoma arising from ovarian endometriosis. Previously, only two reports of primary diaphragmatic CCC were reported, in which coexistent endometriosis with CCC was not histologically proven. We report a case of a 55-year-old postmenopausal woman who was admitted to Kindai university hospital for the examination of a cystic mass with papillary components in the right diaphragm. On her past medical history, abdominal hysterectomy and bilateral salpingo-oophorectomy was performed for high-grade cervical intraepithelial neoplasia, uterine myoma, and bilateral ovarian endometriosis 5 years ago. Unenhanced CT performed 5 years ago, showed a nodular lesion with low density in the right diaphragm, consistent with diaphragmatic endometriosis. Magnetic resonance imaging during this admission, showed a cystic mass with papillary components in the right diaphragm and a T2*-weighted gradient echo imaging showed partial low signal intensity in the papillary components and cyst wall, which was suspected to represent hemosiderin deposition. Based on these serial images, malignant transformation of diaphragmatic endometriosis was suspected. Under, open abdominal combined resection of the mass and part of the diaphragm was performed. Endometriosis implants were detected on the pelvic peritoneum. Histopathological examination revealed clear cell carcinoma associated with endometriosis and hemosiderin deposition in the cyst wall. T2*-weighted gradient echo imaging was useful in the detection of hemosiderin deposition caused by the coexistent endometriosis. When a cystic mass with papillary components and cyst wall with hemosiderin deposits are encountered on MR images, malignant transformation of endometriosis is suspected and a detailed medical history should be determined and the possibility of concurrent endometriosis or adenomyosis should be investigated, as should the potential existence of diaphragmatic endometriosis in previous images.