Perineurioma (storiform perineurial fibroma)

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Abstract
Four cases of perineurioma (storiform perineurial fibroma) arising in the dermis, subcutis, or deep soft tissue have been studied. Two patients were female and two were male with ages ranging from 19 to 45 years. One lesion each arose on the chest wall, shoulder, neck, and elbow. Follow‐up information in three patients revealed no recurrence. Histologically, the neoplasms were circumscribed but non‐encapsulated lesions and were composed of spindle cells with elongated bipolar cytoplasmic processes, inconspicuous fusiform nuclei and well‐defined palely eosinophilic cytoplasm. These cells were arranged in whorls or lamellar‐like structures and often demonstrated a storiform growth pattern. In areas, the tumour cells appeared larger with more rounded nuclei. Immunohistochemically, most of the tumour cells stained positive for epithelial membrane antigen and vimentin, but failed to stain for S‐100 protein, neurofilament, desmoplakin, and CD34. Ultrastructurally, two cases showed fusiform tumour cells with long, thin cell processes separated by abundant collagen bundles. Tumour cells were covered by discontinuous external lamina, showed many pinocytic vesicles and occasionally desmosome‐like structures. The morphology and EMA immunopositivity of perineurioma are similar to meningioma, especially to cutaneous meningioma type II. We believe that perineurioma and meningioma are closely related, but morphologically distinguishable, neoplasms.