pTis = mucosa only;
pT1 = invades submucosa;
pT2 = invades muscularis propria;
pT3 = penetrates through muscularis propria into subserosa or pericolorectal tissues;
pT4a = tumor penetrates to surface of visceral peritoneum;
pT4b = tumor directly invades other organs/structures.
Use yp prefix for post-treatment.