Tissue eosinophilia in oral and cutaneous squamous cell carcinoma and normal oral and cutaneous tissues

Introduction: Eosinophils produce proteases that stimulate invasion in cancers. Due to the more malignant potential of oral squamous cell carcinoma (OSCC) compared to cutaneous squamous cell carcinoma (CSCC), the aim of the present study was to compare tissue eosinophilia between OSCC and CSCC samples to understand whether tissue eosinophilia play a role in different biological behavior of OSCC and CSCC. Also, we assessed the relation between clinical stage and mean eosinophil counts. Materials and Methods: This cross-sectional study included histopathological slides of 30 OSCC, 30 CSCC, 15 normal skin and 15 normal oral mucosa samples. The mean number of eosinophil per square millimeter (eos/mm2) was calculated and the severity of tissue eosinophilia was accordingly categorized into absent/mild and sever. Clinical stages of OSCC and CSCC samples were extracted from archived files. Results: There was significant relationship between mean eosinophil count and clinical stage in both OSCC and CSCC groups (P<0.0001).The differences of mean numbers of eos/mm2 in OSCC and CSCC groups compared to normal groups were significant (P = 0.001 and P = 0.001, respectively), but when we compared OSCC and CSCC groups, the difference was not significant. OSCC and CSCC groups showed significant difference in severity of tissue eosinophilia compared to normal groups (P=0.005 and P =0.004, respectively), but in comparison of OSCC and CSCC groups, the difference was not significant. Conclusion: Intense tissue eosinophilia is correlated with stromal invasion in OSCC and CSCC samples as seen in advanced clinical stage. Different biological behaviors of OSCC and CSCC do not depend on eosinophils and other factors can be involved.