NCAM1 and plexiform neurofibroma: IHC results did not show statistically significant patterns of expression of S-100 protein between the schwannoma and neurofibromas groups (p=0.75). CD56 protein was expressed strongly (3+) in 90% of cases of schwannoma and negative in 86% of neurofibromas, the differential expression between the two groups was found to be statistically significant (p <0.0001).