Rare benign tumor of brown fat
Merkel (1906)
Synonyms: lipoma of immature adipose tissue, lipoma of embryonic fat, fetal lipoma
Most common site - thigh (30%)
Slow growing painless mobile warm mass
30-40 years
Encapsulated
Radiograph - lucent mass with no osseous abnormalities or mineralization.
US - well defined hyperechoic mass with hypervascularity.
Arteriovenous shunting has been reported and hence core needle biopsy is relatively contraindicated especially in deep lesions
CT and MR - well-defined inter/ intramuscular/subcutaneous/retroperitoneal heterogenous lesion. Prominent branching and serpentine high or low flow vascular structures often seen. Usually enhance. Hence difficult to differentiate from well differentiated liposarcoma.
Bone scintigraphy - moderate uptake on blood pool images and mild uptake on static images
Surgical resection, no local recurrence, no malignant change
References:
Murphey MD et al. Benign Musculoskeletal Lipomatous Lesions. RadioGraphics 2004;24:1433-1466
