KRT19 and neoplasm: Four, primary clear cell carcinoma of the gallbladder, a subtype of primary adenocarcinoma of the gallbladder with a low incidence that is more common in women, often accompanied by gallstones, a tumor diameter of 2 cm to 4 cm growth in the gallbladder lumen without invading the muscular layer and serosa, with >50% clear cells, mixed with ordinary adenocarcinoma morphology, and characteristic small vascular reticular septa visible between tumor cells; it can be diagnosed based on immunohistochemistry for PAX8 (+), CK7 (+), CK19 (+) and vimentin (-) [13,14].