Eosinophilic ulcer of the oral mucosa. Report of 38 new cases with immunohistochemical observations.

Eosinophilic ulcer of the oral mucosa (traumatic eosinophilic granuloma) mimics oral cancer clinically and is occasionally misdiagnosed as lymphoma on microscopic examination. Trauma is believed to play a role in its development, but its exact pathogenesis is not known. The demographic, clinical, and histologic features of 38 previously unreported cases of eosinophilic ulcer of the oral mucosa are reviewed. Nine representative cases were studied immunohistochemically. Microscopically, the lesions contained a polymorphic inflammatory infiltrate extending deep into the submucosa, underlying muscle, and salivary glands. Numerous eosinophils and large mononuclear cells with pale nuclei and frequent mitoses were seen in all lesions. Lymphocytes, histiocytes, plasma cells, granulocytes, and mast cells were also present. Immunohistochemical stains showed that the lymphocytic infiltrate was composed predominantly of T cells. T-cell-specific antigen-presenting cells were more numerous than the non-antigen-presenting cell type. The large cells with pale nuclei stained positively only for vimentin; the possible myofibroblastic nature of these cells is discussed. Although trauma might have an etiologic role, the pathogenesis of eosinophilic ulcer of the oral mucosa is probably T cell mediated.