Benign neural tumors of the oral cavity: a comparative immunohistochemical study.

To determine if immunohistochemistry can be used as adjunct to the diagnosis and classification of oral benign neural tumors, we stained 77 neurally differentiated tumors with a panel of neural-associated antibodies (S-100 protein, CD57, epithelial membrane antigen, factor XIIIa, CD34, CD68, collagen IV). Using standard histologic criteria, we identified 13 schwannomas, 16 neurofibromas, 23 traumatic neuromas, 16 palisaded and encapsulated neuromas, and 9 granular cell tumors from archived oral pathology specimens. Silver stains showed that neurofibromas, traumatic neuromas, and palisaded and encapsulated neuromas consistently contained axon filaments. Although all neural tumors contained S-100-positive cells, schwannomas and palisaded and encapsulated neuromas contained the most. All tumors expressed CD57; traumatic neuromas were stained intensely and the others stained weakly. The consistent epithelial membrane antigen capsular staining of schwannomas and the absence of factor XIIIa-positive dendritic/spindle cells helped distinguish these tumors from others. Many CD34-positive cells were found in schwannomas, and few were found in palisaded and encapsulated neuromas. Variable numbers CD68-positive cells were seen in all neural tumor types; some of these cells appeared to be macrophages and mast cells, but many were thought to be Schwann cells expressing this antigen. Collagen IV staining, apparently representing basement membrane, was generally a feature of all benign neural tumors. The immunophenotype of the granular cells of the GCTs was S-100+, CD57+, and collagen IV+ supporting the putative neural origin of these tumors. We conclude that neural origin/differentiation of a connective tissue tumor can be confirmed with stains for S-100 protein, epithelial membrane antigen, CD57, and collagen IV. Staining patterns and intensities associated with the panel of antibodies tested can be useful in tumor classification.