Immunoreactivity of granular cell lesions of skin, mucosa, and jaw.

Granular cell lesions from many different sites share similar light and electron microscopic features. Immunologically, however, these lesions do not appear to be a homogenous group. This study determines the extent of immunologic heterogeneity of granular cell lesions from a wide variety of sites in skin, mucosa, and jaw. Thirty-one granular cell lesions (26 granular cell tumors [GCT] and five other granular cell lesions) from 18 different sites were evaluated immunohistochemically for keratins, vimentin, desmin, muscle actin, ACT, HLA-DR, and S-100 protein. Paraffin-embedded sections were utilized with an avidin-biotin complex immunoperoxidase technique. Except for ameloblastomas, all lesions were negative for keratin and positive for vimentin. All lesions were negative for desmin and actin. Positive ACT reactivity was found in one of seven GCT of tongue, a colonic lesion, a nose lesion, and a granular cell ameloblastic fibroma. All lesions were positive for HLA-DR except a few in which fixation appeared inadequate. S-100 immunoreactivity was found in all lesions except the congenital epulis, a GCT of the skin of the nose, a colonic lesion, and the odontogenic tumors. The antigenic profile of GCT of skin and mucosa is consistent with Schwann cell origin. However, some GCT and other granular cell lesions appear to be derived from macrophages, epithelial cells, or other cells. The expression of HLA-DR by granular cells is believed to be unrelated to cellular origin but rather to some common immunologic function.