Primary leiomyosarcoma of bone

OBJECTIVE, This study describes radiographic and MR imaging features of pri mary lei omyosarcoma of bone. SUBJECTS AND METHODS. Twelve patients (five men and seven women, 39-79 year s old) who were treated at two oncology centers for primary leiomyosarcoma of bone involving the femurs, tibia, ilium, and inferior pubic ramus were s tudied. None of the patients had preexisting disease or disease elsewhere a t the time of diagnosis. Pathologic diagnosis was obtained in all patients. RESULTS. Radiographs of all patients showed a matrix that was exclusively o steolytic. In long bones (seven patients), the tumor had an average length of 11 cm (range, 7-17 cm) and revealed an elongated configuration. In the p elvis (five patients), the average length of the tumor was 10 cm (range, 4- 15 cm), MR imaging confirmed an intramedullary lesion in all patients, with extension into the soft tissues in eight patients and no identifiable soft -tissue mass in the remaining four patients. Four of the five pelvic tumors had a prominent soft-tissue mass, whereas only four of the seven long bone lesions revealed a soft-tissue mass that was, in all instances, small. The tumor was hypointense on T1-weighted images and showed heterogeneous signa l intensity on T2-weighted conventional and fast spin-echo sequences. We sa w low signal intensity (short T2) in eight patients and homogeneous hyperin tense signal intensity in one patient. In the remaining three patients, T2- weighted spin-echo sequences obtained with fat saturation showed high signa l intensity (long T2) in the tumors. CONCLUSION. Primary leiomyosarcoma of bone is a rare tumor that on radiogra phy reveals no matrix and on MR imaging reveals areas of T2 shortening in r elation to fat on conventional and fast spin-echo sequences.