Layers of the bowel wall

Mucosa
Muscularis mucosae
Submucosa
Muscularis propria
Subserosa
Serosa

Dukes staging

A:

B: Penetrating wall (including touching wall)

C1: Local nodes/peri-rectal nodes

C2: Apical nodes

D: Distant spread

Dukes staging system does not take into account the lesion that extends laterally (rather than through wall). Therefore one can have a massive superficial tumour.