Peritoneal metastasis in colon cancer is staged as
T1 Invades submucosaT2Invades muscularis propriaT3Invades through the muscularis propria into perirectal tissuesT4aInvades through the visceral peritoneumT4bDirectly invades to adjacent organs or structuresN1aOne node positiveN1b2-3 nodes positiveN1cNo regional lymph nodes positive, but there are tumour deposits in the subserosa, Mesentery or non-peritonealized pericolic/ perirectal/ mesorectal tissues N2a4-6 lymph nodes positiveN2b7 or more lymph nodes positiveM1aMetastasis to one site or organ, without peritoneal metastasisM1bMetastasis to 2 or more sites or organs without peritoneal metastasisM1c Metastasis tothe peritoneal surface (alone or along with other site/organ)Ref: AJCC 8e
M1a
M1b
M1c
M1d
G.I.T