Tumour Associated Tissue Eosinophilia in Oral Squamous Cell Carcinoma by Special Histochemical Analysis of Tissue Eosinophilia using Congo Red Staining

Introduction: Tumour Associated Tissue Eosinophilia (TATE) is an important phenomenon occurring in the tumour microenvironment and has a pivotal role. TATE is defined as “eosinophilic stromal infiltration of a tumour not associated with tumour necrosis or ulceration”. The exact role of TATE in malignancies is yet unclear but studies have shown that TATE usually has a favourable outcome in head and neck Squamous Cell Carcinoma (SCC). Therefore, more studies are needed to substantiate this data. Aim: To compare TATE between normal epithelium and Oral Squamous Cell Carcinoma (OSCC) and compare TATE between the histological grades of OSCC. Materials and Methods: A retrospective study was conducted at Dr. BR Ambedkar Medical College, Bangalore, Karnataka, India, from June 2019-January 2021 which included 50 cases, 10 from normal mucosa and 40 histopathologically diagnosed cases of OSCC. 1% congo red solution was used to stain 4 μm thick sections. The sections were examined at a high magnification (40X) and 10 microscopic fields were examined in succession for eosinophils. The average number of eosinophils observed were compared using univariate analysis, which included the Analysis of Variance (ANOVA) test and the Chi- square test and a p-value of 0.001 was considered statistically significant. Results: The mean value of tissue eosinophils increased in OSCC compared to normal mucosa, according to present study findings. When comparing different grades of carcinoma, statistical analysis revealed that well differentiated squamous cell carcinoma had a greater TATE than other grades, which was statistically significant (p-value <0.001). Conclusion: The higher eosinophil count in well differentiated OSCC compared to the other grades could be associated with a better clinical outcome for the patient. In OSCC, TATE can be utilised as a predictor of a good prognosis.