CNP and perineurioma: In the current study, perineurioma was excluded from the differential diagnosis list due to the lack of the typical whirling with a concentric arrangement of neoplastic cells around a central axon (i.e., “pseudo-onion bulbs”) [1,44,50], while the patchy distribution of S100 protein and CNPase expression were suggestive of a neurofibroma rather than a Schwannoma [48,51,67].