Background and purpose: Mast cells as the multi-functional and complex cells play a key role in tumor progression. Due to the higher malignant potential of Oral Squamous cell carcinoma (OSCC) compared with cutaneous squamous cell carcinoma (cSCC), the purpose of this study was to compare the mast cells count in squamous cell carcinoma of the skin and oral cavity and evaluate their correlation with the degree of differentiation of these tumors.

Materials and methods: In this retrospective study, 30 cases of OSCC and 30 cases of cSCC were investigated. Toluidine blue staining was used to identify the number of mast cells in samples. Data was analyzed in SPSS (V.21) applying Mann-Whitney, Kruskal Wallis and Pearson correlation coefficient tests.

Results: The mean count of mast cells in OSCC and cSCC were 46±29.68 and 63.66±40.85, respectively, indicating a significant difference (P=0.012). The mean counts of mast cells in grade I OSCC and grade III of cSCC were higher than those of other grades but the differences were not statistically significant (P>0.05).

Conclusion: The average number of mast cells in oral squamous cell carcinoma was less than that in cutaneous squamous cell carcinoma. It seems that other factors such as cytokines and chemokines released from tumor cells and inflammatory cells other than mast cells are effective in the progression of oral squamous cell carcinoma.