Giant cell fibroblastoma: a report of three cases with histologic and immunohistochemical evidence of a relationship to dermatofibrosarcoma protuberans.

Abstract

Giant cell fibroblastoma (GCF) is a rare mesenchymal neoplasm, which is classified as a fibrohistiocytic tumor of intermediate malignancy owing to its propensity for local recurrence, although metastasis has not been documented. Prior reports have linked GCF to dermatofibrosarcoma protuberans (DFSP), given overlapping clinical and histologic features. This report documents three additional cases of GCF that further support the contention that this lesion is histogenetically related to DFSP. All three lesions occurred on the trunk of patients whose ages were 4, 28, and 38 years. One case that histologically resembled a GCF on initial excision recurred with areas of both GCF and DFSP. A second recurrence was composed entirely of DFSP. Another case contained areas of both GCF and DFSP, as well as a focus that was felt to be undergoing fibrosarcomatous change. The third case consisted entirely of GCF. Immunohistochemically, all three lesions showed intense immunoreactivity for CD34 in the GCF component. CD34 also strongly marked the cells in those cases with a DFSP component. Although GCF may not represent the "juvenile form" of DFSP, as previously suggested, the evidence strongly supports a histogenetic relationship between these two lesions, even though the cell of origin remains obscure.