Mast cells in oral lichen planus.

Biopsies from lichen planus affected oral mucosa were compared with biopsies from healthy oral mucosa, in terms of the number of mast cells, their location and their morphological alteration at the light microscopic and electron microscopic level. In comparison with the normal oral mucosa an increased number of mast cells was found below the subepithelial infiltrate. This difference was statistically highly significant (p less than 0.001). In the deeper part of the infiltrate mast cells were found to contain granules which presented an altered morphology upon electron microscopic examination. These cells had many of the ultrastructural changes that have been reported for mast cells undergoing degranulation. The present morphological observations suggest that mast cells participate in the recruitment of lymphocytes to the subepithelial infiltrate.