[A case of primary leiomyosarcoma of tibia with multiple skeletal metastases]

To describe the first case of leiomyosarcoma of the tibia with multiple skeletal metastases in China. A 31-year-old woman was referred to Peking University People's Hospital for evaluation of a lesion on the proximal left tibia. The radiographic examination showed the lesion had a moth-eaten destructive appearance with ill-defined border and soft tissue extension. The tumor is isointense to muscle on T1-weighed images and heterogeneous and of high signal on T2-weighed images. Technetium-99m bone scintigraphy demonstrated multiple markedly increased skeletal radioisotope uptake. The tibia lesion was surgically removed. Microscopically, tumor cells consisted of spindle shaped cells, arranged in bundles, with cigar-shaped and blunt-ended nuclei. Immunohistochemistry revealed that the tumor cells were positive for smooth muscle antigen (SMA) and caldesmon. It should be cautious to make the diagnosis of leiomyosarcoma arising in bone. After excluding metastasizing leiomyosarcoma of gastrointestinal tract, urinary system and uterus, the final diagnosis relies on immunohistochemical analysis, however, other spindle cell sarcomas have to be differentially diagnosed.