Table 1.

erbB2 overexpression and gene amplification reported frequencies in tumors of the digestive system

Primary tumor	erbB2 overexpression frequencies	HER2 amplification frequencies	Ref.
Esophageal cancer	4%-22%	4%-14%	[33-36,38,39]
Gastric cancer	13%-22%	10%-18%	[12,41-47]
Colorectal cancer	2%-11%	3%	[48-57]
Biliary tract cancer	5%-76%	1%-8%	[27,75,86,88-90]
Pancreatic cancer	0%-50%	2%-29%	[17-19,64-66,68]
Liver cancer	2%-5%	0-1%	[72-79]