ERBB2 and carcinoma: In tumours of the ampulla, distal bile duct and gall bladder, the frequency of HER2 overexpression has been low, and comparable to pancreatic cancer in a few small studies [16, 17, 23], whereas larger studies have found overexpression in 6–13% of ampullary tumours [27, 28], and 23% and 17% of tumours of the bile duct and gall bladder [29].