A cutaneous case of giant cell angiofibroma occurring with dermatofibrosarcoma protuberans and showing bimodal CD34+ fibroblastic and FXIIIa+ histiocytic immunophenotype.

Abstract

Dei Tos and colleagues in 1995 reported a series of seven distinctive orbital tumors in adults which they named giant cell angiofibroma (GCA). The morphologic features are intermediate between giant cell fibroblastoma and solitary fibrous tumor with a richly vascularized, patternless spindle cell proliferation forming a collagenous or myxoid stroma with pseudovascular angiectoid spaces. The spindled tumor cells have large, rounded nuclei, sometimes with complex folded shape and pseudoinclusions. There also are multi- or mononuclear giant cells, and these tumor cells partly line so-called angiectoid spaces. Cells express human progenitor cell antigen CD34 and vimentin. One case in the buccinator fascia was also noted by the authors, but similar cutaneous lesions are thus far unknown. We report our experience with a polypoid tumor that ocurred on the thigh of a 49-year-old woman that conforms to the description of GCA. The tumor has variegated vessels admixed with patternless spindle and giant cell stroma with angiectoid spaces as well as areas of dermatofibrosarcoma protuberans (DFSP). Most tumor cells express vimentin and CD34, including giant and spindle cells lining angiectoid spaces. Focally up to 40% of the lesional cells express coagulation factor XIIIa with histiocytoid to highly dendritic cytosomes. The DFSP component is composed of admixed CD34+ and FXIIIa+ dendritic cells arranged in a storiform pattern. Tumor cells are negative for actin, desmin, S-100, and cytokeratin. The Ki67 proliferation index is 1% in GCA areas and 3% in DFSP areas; Ki 67 stains mainly fibroblasts. We conclude that this cutaneous GCA is a fibrohistiocytic tumor closely related to and representing a more organoid angioformative analog of GCF, with both being related histogenetically also to DFSP. These lesions represent part of a greater spectrum of fibrovascular tissue patterns, all probably derived from proliferations of interactive microvascular CD34+ fibroblasts and FXIIIa+ histiocytes.