Synchronous multifocal bone sarcomas--a case report and molecular pathologic investigation.

A case of a 54-year-old woman is described who developed synchronously two malignant bone tumors: a dedifferentiated chondrosarcoma in the olecranon and a malignant fibrous histiocytoma (MFH) in the lower tibia. The anaplastic part of the dedifferentiated chondrosarcoma revealed an MFH-like pattern. Myogenous differentiations were not observed in the anaplastic sarcoma cells. The MFH in the tibia showed a storiform-pleomorphic pattern. Single tumor cells showed positivity for M-actin and desmin pointing to myogenous differentiation. DNA-cytophotometry of the dedifferentiated chondrosarcoma showed an aneuploid stem cell line. The MFH in the tibia did not reveal aneuploid stem cells. Staining for p53 protein was negative in both tumors. SSCP analysis and sequencing of the p53 gene in both tumors revealed in the dedifferentiated chondrosarcoma a mutation in exon-8 with the transversion from G to T in codon 294 resulting in a substitution of a stop codon for GLU. The mutation was not observed in the MFH. From these immunohistologic, DNA-cytometric and molecular biologic investigations, we consider it probable that the tumor in the lower tibia is a second highly malignant bone tumor and not the metastasis of the dedifferentiated portion of the dedifferentiated chondrosarcoma in the olecranon.