Context: Papulosquamous lesions are a broad variety of dermatological disorders that encompass non infectious papular and squamous lesions known to have a varied distribution of mast cells. The role of mast cells in the pathogenesis of skin lesions like lichen planus is evident by the increase in their number and morphological alterations of these cells as noted by few authors. Aims: To quantify and evaluate mast cells in various papulosquamous diseases. Methods and Material: A total of 50 cases of papulosquamous skin lesions were retrieved from archives. H & E sections were reevaluated to confirm the diagnosis. Sections from representative blocks were cut to stain with Toluidine blue. They were evaluated for mean number of mast cells by evaluating three 40X high power fields. The mast cells were assessed for mean mast cell number, location, granularity and morphology. Results: Among 50 cases selected 3 were rejected due to insufficient block material. 17 cases of lichen planus(LP), 10 cases of psoriasis vulgaris (PV), 6 cases of discoid lupus erythematosus (DLE), 2 each of pityriasis lichenoid rosaeca, lichen plana pilaris, lichen simplex chronicus and 1 each of 8 other miscellaneous lesions. Mean mast cell number for LP, PV and DLE were 7.5, 8.7 and 5.8 respectively. Degranulation and spindled morphology was observed in 88%, 50% and 100% in LP, PV and DLE. Conclusions: The mast cells present in the lesions can bear influence on the pathogenesis of papulosquamous lesions by release of mediators to induce histological alteration characteristic of these lesions.

Keywords: Mast Cells; Papulo-Squamous Lesions; Skin.