Tumour-Associated Tissue Eosinophilia in Oral Squamous Cell Carcinoma- A Boon or a Bane?

The infiltration of tumour stroma by eosinophils, Tumour-Associated Tissue Eosinophilia (TATE) is known to modulate the evolution of Oral Squamous Cell Carcinoma (OSCC). Identification of eosinophils in the inflammatory stroma has been proven to be an important factor in prognostication of malignant tumours including cancers of mouth, oesophagus, larynx, pharynx, breast, lung, intestine and genitourinary tract.

Our study aimed to assess the role of TATE as a prognosticator in OSCC as visualized by Haematoxylin and Eosin (H&E) and congo red staining.

Thirty histologically-proven cases of OSCC were retrieved from the archives of Department of Oral Pathology, Manipal College of Dental Sciences, Mangalore, Manipal University, Karnataka, India. Two serial sections of 4μm thickness were made and subjected to routine staining with H&E and modified congo red staining, where eosinophil granules stained red and nuclei stained blue. In 40x magnification, 10 HPF at invasive tumour front were assessed for counting eosinophils by placing a 49 square grid (measuring 0.0289 sq mm).

The TATE was compared with the prognosticators using Mann-Whitney U-test. The grades of carcinoma were correlated with TATE using Kruskal-Wallis test followed by Post-hoc Bonferronis correction. Agreement of the number of eosinophils counted in the two staining techniques (H&E and Congo red) in OSCC was achieved using interclass correlation coefficient, and Friedman's test. A value of p< 0.05 was considered statistically significant.

Our results showed that tissue eosinophil counts were higher in well-differentiated cases of OSCC, cases with lymph node involvement, decreased survival, without margin involvement and in cases that did not recur. H&E stain showed significantly better visualization of eosinophils resulting in higher eosinophil counts than when seen with Congo red (p=0.008).

Thus, TATE can be used as a surrogate marker in prediction of survival and recurrence in OSCC. H&E proved to be a better stain for evaluation of eosinophils.