Pathologic research update of colorectal neuroendocrine tumors

Table 2 Proposed staging system for rectal and colon NETs[62,63]

	Rectal	Colon
Depth of invasion and size
T1	Up to and into muscularis propria, ≤ 1 cm	Any depth of invasion, ≤ 1 cm
	Up to muscularis propria, > 1 to ≤ 2 cm	Up to or including muscularis propria, > 1 to ≤ 4 cm
T2	Beyond muscularis propria, ≤ 1 cm	Beyond muscularis propria, > 1 to ≤ 4 cm
	Into muscularis propria, > 1 to ≤ 2 cm	Up to or including muscularis propria, > 4 cm
	Up to and into muscularis propria, > 2 cm
T3	Invasion beyond muscularis propria, > 1 cm	Beyond muscularis propria, > 4 cm
Lymph node
N0	No lymph node metastasis
N1	Regional lymph node metastasis
Distant metastasis
M0	No distant metastasis
M1	Distant metastasis
Stage
I	T1; N0; M0
II	T1; N1; M0 or T2; Any N; M0
III	T3; N0; M0 or T3; N1; M0
IV	Any T; Any N; M1