Histology and Immunohistochemistry Localization of ESAT6 Expression on Caseous and Non-caseous Granuloma of Extrapulmonary Tuberculosis

Abstract

Background: TB diagnosis by histopathological examination is based on the presence of epithelioid granuloma with caseous necrosis. The absence of caseous necrosis will make it difficult to distinguish between TB and non-TB granulomas. The use of ESAT-6 as a confirmative examination of TB immunohistochemically has not been fully used nor are there sufficient data showing the features of ESAT-6 immunolocalization in a granuloma. The purpose of the study was to identify differences in ESAT-6 expression in caseous and noncaseous EPTB granulomas.Methods: A cross sectional study using 66 samples of formalin fixed paraffin embedded tissues from several anatomical lesions.The samples previously diagnosed as tuberculous granuloma were evaluated histologically and immunohistochemically. Mann Whitney tests were used for statistical analysis. Result: There were no significant differences in histological findings and immunohistochemical staining of ESAT-6 on macrophages of caseous and non-caseous granuloma of EPTB. ESAT-6 protein was expressed on cytoplasm of epithelioid macrophages, foamy macrophages, Langhans type giant cells and some necrosis areas in the granulomas.Conclusions: This study showed that macrophages of caseous and non-caseous granuloma of EPTB expressed ESAT-6 protein in the same way. This finding supports the use of the anti ESAT-6 antibody as a complementary diagnostic test in diagnosing granuloma of EPTB.