Aberrant expression of pyloric gland-type mucin in mucin-producing bile duct carcinomas: a clear difference between the core peptide and the carbohydrate moiety

The authors have recently defined the clinopathological entity of a mucin-producing bile duct tumor (MPBT), and divided MPBT into two distinct subtypes: ‘columnar-type’ and ‘cuboidal-type’ MPBT. Mucin core protein 6 (MUC6), which is present in normal pyloric glands, had higher expression levels in cuboidal-type tumors than in columnar-type tumors. In the pyloric glands, a carbohydrate antigen detected by monoclonal antibody HIK1083 (CA/HIK1083) is also expressed. In order to evaluate the coexpression pattern of MUC6 and CA/HIK1083 in MPBT, expression profiles were evaluated in 38 surgically excised mucin-producing bile duct carcinomas (MPBC; cuboidal-type, n = 15; columnar-type, n = 23), using immunohistochemistry. The staining rate was graded as follows: –