MULTIPLE IMAGINGS TO DIAGNOSE THE CHONDROSSEOUS METAPLASIA WITHIN A LIPOMA NEAR THE KNEE

A 61-year-old man with a slow-growing, painless mass in the area of th e right knee underwent radiographic, computed tomographic (CT), arthro graphic, arteriographic, and bone scintigraphic imaging studies. Scint igraphy showed an area of intense uptake in the anterolateral part of the knee; the uptake of the knee was much higher than that of the knee joints, but the area was not connected to the joint. Radiographic fin dings suggested an osteocartilaginous mass which was seen to contain l ow-density fatty tissue on the CT exam. Arthrography revealed that the re was no connection of the mass to the knee joint. Arteriography show ed a mildly vascularized tumor mass. Upon removal, the mass was well e ncapsulated, measuring 10 x 7 x 7 cm, and consisted of integrated nodu les of bone, cartilage, and fat tissue. Microscopic examination confir med lipoma with osteochondromatous metaplasia. The intense uptake in t he lipoma near the bone or joint on the bone scan and multiple osteoch ondromatous nodules shown on CT may serve as characteristic features o f the rare chondrosseous metaplasia within a lipoma.