Intra-osseous Lipoma- Calcaneus

Intra-osseous lipoma is an extremely uncommon entity despite the large amount of adipose tissue present in the bone marrow. The condition was first described by Wehrsing. •Benign tumor composed of mature, adult fat •Adults between 30-60 •Males slightly more than females •Frequent skeletal locations include ◦Proximal femur, intertrochanteric region (34%) ◦Base of neck of calcaneus (8%) ◦Tibia (13%) ◦Ilium (8%) Clinical Findings •Found incidentally 1/3 time •Pain •Tenderness •Swelling Milgram's Classification Intraosseous Lipomas Stage Description 1 Viable fat without necrosis 2 Viable fat with necrosis and dystrophic calcification 3 Extensive fat necrosis, calcification, cysts Imaging Findings •On MRI ◦Fat in lipoma is isointense with subcutaneous fat on T1 ◦Low signal on T1 with fat suppression •On conventional radiographs ◦Lucent lesion with sclerotic margin ◦Central sclerotic bulls-eye (pathognomonic) ■Cockade image-resembles the badge or rose worn upon a hat ◦May be associated with mild expansion of long bone Differential Diagnosis •Not to be mistaken for normal areas of lucency in calcaneous and proximal femur •Osteonecrosis Treatment •None usually needed if asymptomatic •Curettage and bone grafting for symptomatic lesions Complications •Recurrence and malignant transformation is very rare Prognosis •Frequently disappears spontaneously