Quantification of mast cells in reactive oral lesions – A clue to the morphologic diversity Saurabh Shekar, Punnya V Angadi Indian Journal of Health Sciences and Biomedical Research (KLEU) 2019 12(2):123-126 OBJECTIVE: Inflammatory fibrous hyperplasia (IFH), pyogenic granuloma (PG), peripheral ossifying fibroma (POF), and peripheral giant cell granuloma (PGCG) are common oral soft-tissue reactive lesions that correspond to excessive connective tissue proliferation as a reaction to trauma or irritational factors local to the oral cavity. These lesions have specific differences in their histopathologic appearances and behavior in spite of having common etiologic factors. Mast cells (MCs) are immune-regulatory cells that have an important role to play in oral inflammation and have also been associated with tissue remodeling and fibrosis in various disorders. METHODOLOGY: MCs were stained with toluidine blue in cases of IFH (20), PG (20), PGCG (20), and POF (20) along with normal gingiva tissue as control (5) for quantification and comparison among them. RESULTS: The mast cell count was low in normal mucosa but a progressive increase was seen from PGCG to IFH to POF with maximum mast cells were evident in PG. There was a significant difference noted in the MC counts between the normal mucosa and the oral reactive lesions (P < 0.05). However, the difference in the MC count did not reach statistical significance among the reactive lesions (P = 0.400). CONCLUSION: MCs emerged as significant players in the pathogenesis and histopathologic diversity of oral reactive lesions by their effects on fibroblasts and endothelial cells.