Kaposis sarcoma is an AIDS defining illness. It is more common in homosexual men than iv drug users. It commonly affects the skin, when the CD4 levels are less than 200. It can affect any organ of the body , including femur, pelvic bones, shoulder and chest wall. It can be solitary or multiple. It can be secondary to local exension of a cutaneous lesion or very rarely primarily osseus, which is more common i Africa.The lesions have poor transition margins, geographical or permeative pattern of destruction. Periostitis is seen very rarely. Soft tissue extension can be seen.CT and MRI are useful for further characterisation.  Bone scan is cold. Increased uptake is seen in 99 Tc labelled RBC scans. Normal uptake is seen in gallium scan and increased uptake is seen in thallium 201 scans.

X ray of the right hip shows an expansile lytic lesion in the femoral neck.

CT scan shows the mass in the right femoral neck, with extension into the anterior soft tissue space.

Bone scan shows increased uptake in the right femoral neck and head. Increased metastatic uptake is also seen in the mid shaft of the right femur.