Giant cell fibroblastoma. New histological observations.

Giant cell fibroblastoma is a rare mesenchymal neoplasm of unknown origin and uncertain clinical course. The neoplasm has been considered by some authors as a juvenile variant of dermatofibrosarcoma protuberans. We report a patient with giant cell fibroblastoma, now 28 months following surgical removal, in which the neoplasm was characterized histologically by a proliferation of spindle-shaped cells intermixed with pseudovascular channels called "angiectoid spaces." The spaces were lined by large cells with pleomorphic nuclei intermixed with multinucleated cells. Immunohistochemically, the tumor stained diffusely for vimentin and CD34, a surface glycoprotein expressed by some mesenchymal neoplasms including dermatofibrosarcoma protuberans. We postulate a mechanism of formation of the angiectoid spaces based on histopathological findings in serially sectioned portions of the neoplasm. Positive staining of tumor cells for CD34 supports a possible relationship of the neoplasms with dermatofibrosarcoma protuberans.