Giant cell fibroblastoma associated with dermatofibrosarcoma protuberans: a case report.

A case of congenital giant cell fibroblastoma (GCF) associated with dermatofibrosarcoma protuberans (DFSP) in a 1.5-year-old girl is reported. The GCF component was characterized by a mixed proliferation of fibroblastic cells and multinucleated giant cells and sinusoid-like spaces. The DFSP component, which was spatially distinct from the GCF region, was composed of short spindle-shaped cells arranged in a storiform pattern. Mitotic figures were frequently identified in the DFSP area but not in the GCF region. Immunohistochemically, tumor cells in both components were positive for CD34. The Ki-67 labeling index of the DFSP area (4.9%) was markedly higher than that of the GCF (0.5%). Ultrastructurally, spindle-shaped tumor cells in both components, as well as giant cells, were fibroblastic cells that frequently exhibited multilobulated nuclei. This case illustrates the close histogenetic relationship between GCF and DFSP, although the degree of proliferative activity is much higher in the DFSP area.