A, Axial T1-weighted MR image shows the fluid within the cystic part of the mass. It is of high T1 signal intensity (asterisk) and does not suppress with fat suppression and is consistent with blood. B, Axial T2-weighted MR image shows the solid mural nodularity of the cyst wall at the anterosuperior aspect (white arrow). It is strikingly similar to the decidualized endometrium (between black arrows) of the gravid uterus, both with respect to signal intensity and texture.