The aim of this study was to determine the prevalence of c-kit (CD117) and Her-2/neu expressions in malignant bone and soft tissue tumors and to identify a possible predictive role in patients with these malignancies.

A retrospective study was conducted on 40 archival paraffin-embedded tissue specimens of patients with 32 malignant bone tumors (23 osteosarcomas, 9 chondrosarcomas) and 8 synovial sarcomas. The gene expressions levels were evaluated by immunohistochemistry.

C-kit expression was observed in 13 out of 23 osteosarcoma patients (56.5%), 4 out of 9 chondrosarcoma patients (44.4%) and 4 of 8 synovial sarcoma patients (50.0%). In particular, the relationship between c-kit expression and gender (p=0.044), a pulmonary metastasis (p=0.044), and the tumor cell grade (p=0.023) in osteosarcoma were found to be statistically significant. On the other hand, Her-2/neu expression was not found in any of the 40 cases under study.

These results suggest that the c-kit expression appears to play an important role in the development of a malignant bone tumor and synovial sarcoma. In particular, it should be noted that c-kit expression is found frequently in an osteosarcoma with a pulmonary metastasis. In this respect, the tyrosine kinase inhibitors can be considered to be significant in the treatment of a malignant bone tumor and a synovial sarcoma. However, Her-2/neu does not appear to play any significant role in these malignancies.