65-year-old female with history of left thigh mass. Please evaluate for extent of disease and abnormalities. There is a large mass of predominantly fat signal intensity involving the posterior left thigh and extending into the left buttock. The superior extent of the mass is at the level of the origin of the left gluteus maximus muscle from the upper iliac wing. Here the mass lies between the gluteus maximus muscle and the gluteus medius muscle, deep to the iliotibial band. A small lobule of the mass extends beneath the left piriformis muscle into the sciatic notch. An additional small lobule extends medially just below the ischiofemoral space, with poor visualization of the quadratus femoris either due to infiltration or mass effect. Although the mass is of predominantly fat signal intensity, there are poorly defined whorls of nonadipose tissue within the mass, particularly anteriorly, some of which show enhancement following gadolinium administration. Several vessels are also noted within the mass. There is a bandlike focus of low signal intensity within the mass posteriorly that does not appear to enhance, perhaps representing fibrous tissue or mineralization.As the mass enters the upper thigh, it assumes a bilobed configuration. The smaller anterior lobe continues distally deep to the iliotibial band, tapering along the lateral margin of the vastus lateralis; it terminates approximately 4 to 5 cm below the level of the base of the greater trochanter. The larger posterior lobe extends inferiorly into the mid and distal thigh. It lies deep to the peripheral deep fascia, displacing the distal fibers of the gluteus maximus muscle laterally and the hamstring musculature medially. Within the proximal half of the thigh, the mass displaces the sciatic nerve medially, with a nerve coursing along the medial aspect of the mass. The mass terminates distally approximately 12 to 13 cm above the knee joint line. As in the pelvis, the mass is of predominantly fat signal intensity, but also containing thin septae and poorly defined nonadipose elements, some of which enhance following gadolinium administration. Small vascular structures also courses through the mass. Within the mid thigh, the mass is approximately 14 x 12 cm in greatest transverse dimension. The mass is not included on any single longitudinal image, which limits my ability to obtain an accurate measurement in this dimension; however, based on summative measurements, I estimate the mass to be between 35 and 40 cm in craniocaudal dimension.Pelvis: There is a mass of fat signal intensity at the level of the right hip joint situated between the proximal right sartorius muscle and the iliopsoas muscle. It measures no more than 6 cm in craniocaudal dimension and 2.5 cm in transverse dimension, and likely represents a benign lipoma. There also appears to be asymmetric fatty infiltration of the anterior half of the gluteus minimus muscle. I see no additional masses within the pelvis. Mild osteoarthritis affects both hips and sacroiliac joints. Bone marrow signal intensity is otherwise within normal limits. Although the study was not protocoled for detailed evaluation of the pelvic viscera, I see no gross abnormalities.Left femur/thigh: I see no additional masses within the left thigh. Bone marrow signal intensity of the left femur is normal. I see no edema within the musculature of the thigh. Osteoarthritis affects the left knee, particularly the patellofemoral joint with subchondral cyst formation and edema in the patella. There is also a small knee joint effusion, and enhancement of the synovium suggests mild synovitis of the knee. A few venous varicosities are noted within the soft tissues of the thigh.
Large predominantly fatty mass of the left thigh extending into the left buttock as described above. Based on its size and signal characteristics, this most likely represents an atypical lipomatous tumor (well differentiated liposarcoma). Referral to orthopedic oncology is recommended. Other findings as described above.