Background and Objective: Oral squamous cell carcinoma (OSCC) is the most common oral cancer. The prognosis of OSCC depends on many factors. The stage of the tumor and the condition of the lymph nodes are two important factors in determining the treatment methods and prognosis. Since the identification of clinicopathological indicators, especially the cervical lymph node involvement, can increase the accuracy in estimating the prognosis and adopting the appropriate treatment method, the aim of this study is to compare the frequency of tissue eosinophils in OSCC with and without cervical lymph node involvement (CLNI).
Methods: In this cross-sectional study, 17 OSCC samples with CLNI (group 1) and 17 samples without CLNI (group 2) from the samples registered in the Pathology Department of Ayatollah Kashani Hospital, which were treated by neck dissection surgery, were selected and clinicopathological data were extracted. Then, in order to determine the number of tissue eosinophils, slides prepared with Congo red staining were blindly examined by two oral pathologists with an optical microscope.
Findings: 88.2% of the group with cervical lymph node involvement had lymphovascular involvement, while 88.2% of the group without lymph node involvement did not have lymphovascular involvement, and this significant difference was reported (p<0.001). Also, the mean number of tissue eosinophils in group 2 (19.95±5.67) was higher than group 1 (7.36±3.39), indicating a significant relationship with CLNI (p=0.039), but no significant relationship was found with any clinicopathological parameters. 
Conclusion: According to the results of this study, the number of tissue eosinophils is an important prognostic factor in OSCC, and it can be used to better evaluate patients and provide more appropriate treatment.