Giant cell fibroblastoma (GCF) is a rare tumor considered to be a variant of dermatofibrosarcoma protuberans (DFSP) with similar clinical behavior and molecular features. It is a slow-growing tumor most commonly found on the trunk and proximal extremities. It is not known to metastasize but can be locally aggressive and has a high rate of local recurrence. GCF harbors the same t(17;22) chromosomal translocation as DFSP that places the platelet-derived growth factor beta chain gene (PDGFB) under control of the collagen type I alpha 1 gene (COL1A1) promoter. Hybrid lesions may occur containing features of both GCF and DFSP. In addition, cases of GCF recurring as DFSP and vice versa have been reported in the literature.

GCF notably differs from DFSP in patient demographics and histologic features (see Best Tests section). GCF predominantly occurs in infants and children younger than 5 years, with a strong predilection for males.