Hybrid peripheral nerve sheath tumors: Schwannoma-perineurioma and neurofibroma-perineurioma. A report of three cases in extradigital locations.

We present three cases of subcutaneous tumors with hybrid features of schwannoma-perineurioma (one case) and neurofibroma-perineurioma (two cases), which occurred in two women aged 50 and 52 years and one man aged 52. Locations included the scapular area, skin overlying breast and knee area. The tumors were 1.5, 4 and 5 cm in largest diameter. None of the patients had signs of neurofibromatosis. All tumors were surgically removed, and patients remained disease-free for 1 to 4 years. The classification of the lesion into schwannoma-perineurioma and neurofibroma-perineurioma rested on histopathological and immunohistochemical findings. An ultrastructural study was performed in one case of neurofibroma-perineurioma. All cases were studied for mutation of the NF2 gene, and in one case (neurofibroma-perineurioma) a point mutation was detected in exon 15 of the gene.