BACKGROUND AND OBJECTIVE: It has been mentioned that mast cells may help to tumor invasion. According to different aggressive behavior of oral squamous cell carcinoma (OSCC) compared to cutaneous SCC (CSCC), the aim of this study was to compare mast cells count between OSCC and CSCC to understand the role of them in different biologic behavior of these two tumors.

METHODS: This cross-sectional study consisted of 90 samples including 30 cases of OSCC, 30 cases of CSCC, 15 cases of normal skin and 15 cases of normal oral mucosa (as control groups). Number of mast cells was counted under light microscope in 10 successive fields in invasive front of OSCCs and CSCCs at 400X magnification and mean mast cells count/mm² were calculated and compared between studied groups using one way ANOVA statistical test.

FINDINGS: Mean mast cells count in CSCC, OSCC, normal skin and normal oral mucosa groups were 20.31±14.67, 10.41±8.01, 5.10±8.67 and 4.87±2.68, respectively. There were significant differences in mast cell count between CSCC and normal skin groups (p<0.001) and between CSCC and OSCC groups (p=0.002). This difference wasn’t significant between OSCC and normal oral mucosa groups (p=0.337).

CONCLUSION: Lower level of mast cells in OSCCs may reflect less need for activation of mast cells in order to increase angiogenesis in OSCCs .Increase in mast cell density in CSCCs suggests a possible role for mast cell in tumor progression of CSCCs.