TABLE 1.

Mucosal tumours classified according to their depth of invasion along with the corresponding American Joint Committee on Cancer (AJCC) staging

Tumours	Depth of invasion (AJCC staging)
Mucosal
M1	Limited to the epithelial layer (Tis)
M2	Invades the lamina propria (T1a)
M3	Invades into, but not through, the muscularis mucosae (T1a)
Submucosal
SM1	Penetrates the shallowest one-third of the submucosa (T1b)
SM2	Penetrates into the intermediate one-third of the submucosa (T1b)
SM3	Penetrates the deepest one-third of the submucosa (T1b)

Data from reference 15