The clinical and histologic spectrum of cutaneous fibrous perineuriomas

Cutaneous fibrous perineuriomas (CFPs) and the closely related sclerotic perineuriomas are recently reported tumors. We present nine additional cases of CFPs. All tumors were small nodules on the extremities; however, they were not limited to a distal acral location as previously reported. In addition to tabulation of the histologic features, we performed a battery of immunohistochemical stains, including S-100 protein, CD34, cytokeratin, epithelial membrane antigen (EMA), KP-1, and collagen type IV. Histologically, these tumors presented with sharp circumscription of their deep aspect, as previously reported, or were not circumscribed on any side. The cells ranged from plump and spindled with one or more nuclei to thin, elongated, spindled cells with slender nuclei. A variably fibrotic stromal matrix surrounded these components. Immunohistochemical staining showed EMA-positive staining of the cellular component, with collagen type IV-positive staining surrounding the cells. The tumor cells were negative for S-100 protein, factor XIIIa, CD34, cytokeratin, and KP-1. The tumors reported here add to the clinical and histopathologic spectrum of CFPs.