Primary leiomyosarcoma of bone: clinicopathologic, immunohistochemical, and molecular biologic aspects.
BACKGROUND: Primary leiomyosarcoma of bone is a very rare malignant tumor with uncertain pathogenicity. METHODS: The authors studied five cases of surgically treated primary leiomyosarcoma of bone. Clinical histories and radiographic findings were recorded. Regular clinical and radiographic controls were obtained postoperatively. In all cases, immunohistochemical studies were used to confirm the diagnosis. Molecular biologic examinations, using the polymerase chain reaction technique with microsatellite DNA markers from regions of tumor-relevant genes, were performed to determine the stability of the genome or to detect some typical genomic changes. RESULTS: The study included three women and two men, with an average age of 42 years. The tumor was located in the pelvis in two patients, in the femur in two patients, and in the proximal tibia in one patient. All tumors were classified as high-grade tumors (four stage IIB, one stage IIA). Radiographically, all tumors appear as purely osteolytic lesions, with a geographic or moth-eaten appearance and without any sclerotic margin. Three patients underwent limb salvage surgery followed by endoprosthetic replacement. The other two patients required amputation. The mean follow-up was 19 months (range, 8-29 months). Three patients died of disease, with a mean postoperative survival period of 18 months (range, 6-27 months). Four patients developed diffuse pulmonary metastases after an average of 10.5 months. One of those patients responded well to chemotherapy. In all cases, immunohistochemistry showed strong reactivity of the tumor cells for (alpha-SMA and vimentin. Molecular biologic investigations revealed a high rate of genomic instabilities in all of the stage IIB tumors. CONCLUSION: Clinical follow-up suggests that primary osseous leiomyosarcoma has an aggressive biologic behavior. The immunohistochemical studies are useful tools and suggest that osseous leiomyosarcoma arise from the vascular smooth muscle cells within the bone. The molecular biologic findings of a high rate of genomic instability confirm the hypothesis that this rare entity is of an aggressive nature.