73 year-old female with a right hemipelvis retroperitoneal mass extending into the right hip. Again seen is a predominantly fatty mass within the adductor musculature of the right hip extending through the obturator foramen to involve the obturator internus muscle, measuring approximately 12 x 4.5 cm in the transverse dimension and approximately 11.5 cm in the craniocaudal dimension. The mass also appears to extend slightly into the acetabular fossa. We see no invasion of the bone. There are septations within the mass, some of which appear to show mild enhancement. There are additional nonadipose elements within the superomedial aspect of the mass that appear similar to the prior study and may represent small regions of necrosis, but we see no dominant soft tissue nodule to suggest dedifferentiation.The obturator nerve and artery are not well seen below the level of the pubic ramus. The mass results in slight lateral displacement of the right femoral artery and vein. There is also slight posterior displacement of the right sciatic nerve. The bone marrow signal intensity is within normal limits. Degenerative disc disease affects the visualized lower lumbar spine, most pronounced at the level of L3/L4. There is low signal intensity within the uterus which likely represents fibroids, as seen the prior study. There is also a mass with fat signal intensity measuring approximately 2.0 cm within the left adnexal region which may represent a dermoid.
Predominately fatty mass as described above, appearing similar to the prior study. The differential diagnosis includes a lipoma as well as an atypical lipomatous tumor.