[MR appearance of fat distribution in ovarian teratoma: pathologic correlation]

Magnetic resonance (MR) imaging was performed in 45 patients with 52 surgically proved ovarian teratomas. MR findings of these tumors were classified into three types depending on the degree of fatty proportions in the tumor. The majority of teratomas were filled with fatty tissue in the cystic cavity (n = 43, 82.7%). In 5 tumors (9.6%), fatty tissue was seen at the edge or within the cyst wall. Fatty tissue could not be seen in any part of the tumor in 4 cases (7.7%). The tumors without a fatty component on MR images tend to have fewer sebaceous glands and less fatty tissue within the cyst wall than tumors with an abundant fatty component. Demonstration of fatty tissue is pathognomonic for these tumors. However, tumors with a small amount of fatty tissue may be indistinguishable from cystic ovarian tumors on MR images.