Evaluation of lipomatous soft tissue tumors by MR imaging.

Large soft tissue tumors--5 cm or greater--or deep-seated tumors have a greater risk of being malignant than smaller and superficially located tumors (9). In a period of 2 years 43 consecutive patients with lipomatous tumors 5 cm in diameter or greater were examined with MR imaging. The MR findings were correlated to histologic features and diagnosis. Twenty-six tumors were classic lipomas both on MR and at microscopy; 8 lipomas showed other features--some of them raising suspicion of malignancy at MR; all, however, were histologically benign. Nine tumors were considered malignant at MR imaging; all 9 proved to be malignant by microscopy.