Giant cell angiofibroma. A distinctive orbital tumor in adults.

A series of seven cases of a previously unrecognized potentially recurrent tumor occurring in the orbit of adult patients is reported. This lesion shows histologic appearances intermediate between, but distinct from, solitary fibrous tumor and giant cell fibroblastoma of soft tissue. Morphologically it is characterised by a richly vascularized, patternless spindle-cell proliferation containing pseudovascular spaces. Multinucleate giant cells (often of floret type) and cells with large, rounded nuclei are present both in the cellular areas and also lining the pseudovascular spaces. The stroma is variably collagenized or sometimes myxoid. Immunohistochemically, the tumor cells exhibit positivity for vimentin and CD34. Follow-up in five cases (median duration 24 months) revealed local recurrence in one patient and persistent tumor in another. The clinical and morphologic features enable distinction of this lesion from both solitary fibrous tumor and giant cell fibroblastoma, and we suggest the designation "giant cell angiofibroma of the orbit".