Primary osteosarcoma of the uterine corpus: report of a case with immunohistochemical and ultrastructural study.

BACKGROUND: Primary uterine osteosarcoma is extremely rare, with only 15 cases reported in the literature. CASE: A 41-year-old woman presented with abnormal vaginal bleeding due to a large tumor arising from the uterine corpus. Histologically, the tumor showed the features of a malignant mesenchymal neoplasm with osteoid formation and lacked an epithelial component. Immunohistochemical and ultrastructural studies showed no evidence of epithelial differentiation. The tumor was excised and the patient received chemotherapy and radiation therapy postoperatively, but the tumor recurred locally at the 8-month follow-up. CONCLUSION: Osteosarcoma as a primary uterine tumor is exceedingly rare and should be distinguished from carcinosarcoma, which shows different macroscopic and histologic features. Prognosis of this neoplasm is very poor with an average life expectancy of 5 months.