The mucinous type of well-differentiated adenocarcinoma also has a well-known name – malignant adenoma – which is a type of high-grade gastric-type adenocarcinoma.[64] Under the microscope, a large amount of transparent or pale eosinophilic cytoplasm can be seen in tumor cells, along with moderate nuclear atypia and distinct cell borders, similar to adenocarcinoma cells of gastrointestinal origin.[65] GCA tumor cells contain acidic mucin and express immunomarkers similar to gastric mucous cells, such as HIK1083, lysozyme, and pepsinogen II.[66]. This evidence concerns the gene MUC5AC and adenocarcinoma.