No abstract

Extraosseous osteogenic sarcoma is a very rare malignant neoplasm. Out of the more than 400 cases of soft tissue sarcomas on file in our hospital, only 2 were extraosseous osteogenic sarcomas. Both were situated in the thigh. The first case was initially diagnosed as a hematoma and treated by marginal excision. The diagnosis of high-grade osteosarcoma primarily arising in soft tissue was made from histopathologic examination. Radiotherapy of 60 Gy in 30 fractions was given postoperatively. The second patient, primarily diagnosed as having a soft tissue sarcoma, was treated by wide excision. The final pathologic report was high-grade extraosseous osteogenic sarcoma. Adjuvant chemotherapy was given postoperatively. Both patients are alive without local recurrence and distant metastasis at postoperative 90-month and 107-month follow-up, respectively.

Forty-three cases of spindle cell thymoma (medullary, WHO type A) and 38 cases of mixed spindle/lymphocytic thymoma (WHO type AB) were studied for their clinicopathologic and immunohistochemical characteristics. Three histologic patterns of spindle cell thymoma were observed: short-spindled (57%), long-spindled (31%), and micronodular (12%). The short-spindled variant was composed of oval to short spindle cells commonly arranged in a hemangiopericytic or microcystic pattern. The long-spindled variant chiefly consisted of fibroblast-like epithelial cells mimicking fibrohistiocytic neoplasms. The micronodular variant was characterized by small nests of short spindle cells dispersed among a lymphoid stroma with frequent germinal centers. All kinds of spindle cell could be admixed with lymphocyte-rich "cortex"-like areas to constitute mixed spindle/lymphocytic thymomas. Immunohistochemically, the epithelial cells in up to 70% of the short-spindled and long-spindled variants of spindle cell thymoma and 90% of mixed spindle/lymphocytic thymomas were positive for CD20, whereas the epithelial cells in all micronodular spindle cell thymomas were negative. All of the spindle cell thymomas and most of the mixed spindle/lymphocytic thymomas in this study were found in stages I and II. Follow up of the patients did not disclose relapse or mortality directly resulting from the tumors. However, the prognosis of stage I and II spindle cell and mixed spindle/lymphocytic thymomas did not significantly differ from those of stage I and II thymomas of other types by a stage-matched survival analysis. Our data showed that spindle cell and mixed spindle/lymphocytic thymomas are distinctive in histologic pattern and immunohistochemical profile. When interpreted within the context of staging, spindle cell and mixed spindle/lymphocytic thymomas presenting in stages I and II most likely behave in an indolent fashion.

The results suggest that accumulation of the 4977-bp deletion of mtDNA in knee cartilage increases with age and may play a role in the development of idiopathic OA in the knee joint.