Infantile fibrosarcoma--a misnomer?

Two cases of congenital or infantile fibrosarcoma are described that were incompletely excised at the time of primary excision and have not recurred or metastasized after 3 years. The tumors were composed of densely cellular spindle cells with a high mitotic index. Immunohistochemical stains were positive for vimentin but negative for desmin and S-100. The tumor cells were grown in vitro, and a karyotype was obtained. Both tumors had normal diploid modal karyotypes. In addition, fragments of the primary tumor from both cases were injected subcutaneously into nude mice; neither tumor could be heterotransplanted. The clinical course and biologic features of these two tumors suggest that congenital or infantile sarcoma does not have the properties of a malignant neoplasm, and thus the designation of these tumors as a sarcoma may be a misnomer.