Magnetic resonance imaging findings of endometrioid adenocarcinoma of the ovary

Purpose. We assessed magnetic resonance imaging (MRI) features and clinical characteristics of ovarian endometrioid adenocarcinoma. Materials and methods. A total of 31 patients with 39 surgically proven ovarian endometrioid adenocarcinomas were analyzed retrospectively. Histologically, 13 lesions in 12 patients arose from proven endometriomas (group A), and 26 lesions in 19 patients did not coexist with endometrioma (group B). The morphological pattern of the lesion on MRI was classified as a solid or a cystic type: A solid type was defined as a solid component occupying more than half of the lesion; and a cystic type was a cystic lesion with one or more mural nodules. Results. Altogether, 11 lesions in group A were the cystic type on MRI, whereas 24 lesions in group B were the solid type (P < 0.0001). Among the 11 cystic-type lesions in group A, the cysts of 5 lesions were hypointense on T1-weighted images, and the cysts of 6 lesions were hyperintense on T1- and T2-weighted images without "shading." The nuclear grade was higher (P = 0.0028) and the clinical stage more advanced (P = 0.0018) in group B compared to group A. Conclusion. MRI of ovarian endometrioid adenocarcinomas revealed two types: a solid type and a cystic type. The lesions arising from endometriomas tended to be the cystic type on MRI and have a good prognosis. Preexisting endometrioma in this entity rarely showed "shading" on T2-weighted images. © 2007 Japan Radiological Society.