[3] As defined by microscopic histopathology analyses, GCF tumors consist of a few spindle- and/or stellate-shaped cells in a sclerotic (i.e. collagen fiber-rich) background[8] with distinctive dilated blood vessel-like spaces lined by floret-shaped (i.e. small flower-shaped) multinuclear giant cells.
[2] The tumors may infiltrate into and through nearby subcutaneous fat tissue,[2] commonly have intralesional hemorrhages and distinctive perivascular onionskin-like lymphocytes,[6] and occasionally contain nodules of smooth muscle-like cells.
Some GCF tumors have hybrid characteristics with areas resembling DFSP (e.g. immature-appearing[7] spindle- and/or stellate-shaped cells with abnormally dark nuclei arranged in a monotonous cartwheel or whorled pattern[6]).
[2][6] (DFSP-FS tumors consist of rapidly growing bundles of spindle- and/or stellate-shaped cells with vesicle-containing, abnormally shaped nuclei.
The COL1A1 gene, which directs production of collagen, type I, alpha 1 protein, is normally located in band 21.33 on the long (or "q") arm of chromosome 17.
[9] The PDGFB gene, which directs production of platelet-derived growth factor subunit B (PDGFβ), is normally located in band 13.1 on the q arm of chromosome 22.
This translocation is typically balanced, i.e. involving an even exchange of material with no genetic information gained or lost and, ideally, resulting in the formation of a fusion gene which directs production of a fully functional protein.
[8] The diagnosis of GCF depends on its presentation as a dermal tumor that has a characteristic histology consisting of spindle- and/or stellate-shaped CD34 protein-expressing cells, distinctive dilated blood vessel-like spaces lined by floret-shaped multinuclear giant cells, and/or distinctive perivascular onionskin-like lymphocytes and/or intralesional hemorrhages[6] in a collagen fiber-rich background.