Intraepithelial mast cells in gingival lichen planus: an ultrastructural study.

Intraepithelial mast cells, identified by ultrastructural criteria, were seen in lesions of gingival lichen planus. The mast cells were found either singly, interspersed among keratinocytes, or in combination with other mononuclear cell types, especially lymphocytes. The mast cells were seen in regions with relatively normal intercellular spaces, as well as in regions of more severely disrupted keratinocytes. They had cytologic features indicative of active synthesis and release of granules. Moreover, the finding of centrioles in several intraepithelial mast cells, in combination with certain other cytologic features, suggested that these cells might be in an early stage of differentiation. It is speculated that intraepithelial mast cells have a role in the pathogenesis of gingival lichen planus.