{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Cytokeratins are intermediate-filament keratins found in the intracytoplasmic cytoskeleton of epithelial tissue. There are two types of cytokeratins: acidic type I cytokeratins and basic or neutral type II cytokeratins. Cytokeratins are usually found in pairs comprising a type I cytokeratin and a type II cytokeratin. Expression of these cytokeratins is frequently organ or tissue specific. Cytokeratin 20 (CK20) is a low molecular weight type I acidic intermediate filament protein whose expression is restricted primarily to gastric and intestinal epithelium, urothelium, and Merkel cells. It is a major cellular protein of mature enterocytes and goblet cells found in the gastric and intestinal mucosa. According to literature, CK20 is expressed in various malignancies such as adenocarcinomas of the colon, stomach, pancreas and biliary system. It is also expressed in mucinous ovarian tumors, transitional-cell carcinomas of the urinary tract, and Merkel-cell carcinomas."}]}]}