Elastofibroma: a clinicopathologic and immunohistochemical study of seven cases and literature review.

Elastofibroma is a rare fibrous lesion characterized by accumulated abnormal elastic fibers whose etiology remains largely unknown. In this study, we analyzed seven cases of elastofibroma to further explore the characteristics of its cellular composition. Immunohistochemistry was performed for mast cell tryptase, S-100 protein, vimentin, CD34, smooth muscle actin, desmin and collagen type IV. Histochemical staining methods for Gomori's trichrome and Verhoeff elastica-van Gieson were also evaluated. Histopathologically, a haphazard array of collagen, eosinophilic amorphous fibers, and globules in a fibrous tissue was seen. The elastic nature of the fibers was confirmed by elastic stain, and with Gomori's trichrome collagen fibers were also demonstrated. The interspersed spindle or stellate cells were almost consistently positive for vimentin and frequently positive for CD34. Mast cell tryptase-positive cells were present in five of the cases. Collagen type IV immunoreactivity was seen in two cases. No staining was observed with smooth muscle actin, desmin or S-100 protein. Our findings suggest that CD34-positive mesenchymal cells are an integral component of elastofibroma.