IntroductionChronic calculous cholecystitis is the most common and important contributing factor for cholecystectomy across the country, with a prevalence of 2-29%. Cholesterol supersaturated bile plays a major role in stone formation. It is very essential to identify the pathogenesis of stone formation in order to prevent its formation. This study is aimed to evaluate histomorphological features of chronic calculous cholecystitis and to quantitatively evaluate alteration in mucin expression using the combined Alcian blue-periodic acid Schiff (AB-PAS) stain and the combined high iron diamine Alcian blue (HID-AB) stain, to correlate with each other and also with biochemical features of gall stones. MethodsA cross-sectional study of 64 chronic calculous cholecystitis were taken for histomorphological assessment and grading using Hematoxylin and Eosin (H&E) stain and Masson's trichrome stains. Expression of the type of mucins was analyzed using histochemical stains by a standardized scoring system. ResultsA significant positive correlation was observed between an increase in grades of inflammation and fibrosis with an increase in the quantity of sialomucin and neutral mucin in the deep layers of epithelium, and a significant negative correlation was observed between an increase in grades with a decrease in acidic mucin and sulfomucin of both superficial and deep epithelium except sulfomucin in fibrosis. No significant correlation was obtained with muscle thickness, adipose tissue deposition, and epithelial hyperplasia. A higher frequency of mixed-type stones was associated with severe inflammation. ConclusionInflammation and fibrosis were strongly correlated with quantitative alteration and reversal of mucin composition in chronic cholecystitis; hence we conclude that these features play a significant role in the pathogenesis of stone formation. Using Combined AB(2.5pH)-PAS stain and Combined HID-AB(2.5 pH) stain to detect mucin hypersecretion and composition of altered mucin is relatively accurate and cost-effective rather than performing costly immunohistochemical (IHC) markers.