Giant cell angiofibroma of the inguinal region.

Giant cell angiofibroma is a rare mesenchymal neoplasm most commonly arising in the soft tissues near the orbit. Recently, several cases of extraorbital giant cell angiofibroma have been reported. We report the light microscopic and immunohistochemical features of an additional case of extraorbital giant cell angiofibroma arising in the inguinal region that was clinically mistaken for an inguinal hernia. The patient was a 50-year-old woman who presented with a mobile, nonreducible, left inguinal mass. The tumor was 10.8 cm in greatest diameter, was well circumscribed, and appeared to be encapsulated. Histologically, the tumor was composed of a mixture of cytologically bland spindle-shaped cells and ovoid cells of varying cellularity with deposition in a variably collagenous and myxoid stroma. The tumor had prominent, various-sized blood vessels, often with perivascular hyalinization. In addition, scattered pseudovascular spaces filled with an amorphous eosinophilic material were present and lined by spindle-shaped and ovoid cells similar to those found throughout the neoplasm. Rare multinucleated floret-like giant cells were seen. Immunohistochemically, the tumor cells stained strongly and diffusely for both CD34 and bcl-2 while immunostains for S-100 protein, desmin, smooth muscle actin, and muscle-specific actin were negative. There is no evidence of local recurrence or metastasis 3 months following excision of the mass. This report emphasizes the recognition of this unusual tumor in extraorbital sites. We discuss the overlapping histologic and immunophenotypic features with giant cell fibroblastoma and solitary fibrous tumor and raise the possibility that these tumors could represent a histologic spectrum of CD34-positive dendritic interstitial cell neoplasms.