Table 5.

TNM staging principles for the most common rectal neoplasms: anal (anal canal) and rectal (ampulla) carcinoma, carcinoid and gastrointestinal stromal tumors (GIST) according to the current classification of International Agency for Research on Cancer/World Health Organization [42]

	Anal carcinoma	Rectal carcinoma	Carcinoid of the rectum	GIST
T	Primary tumor
TX	Primary tumor cannot be assessed	Primary tumor cannot be assessed	Primary tumor cannot be assessed	Primary tumor cannot be assessed
T0	No evidence of primary tumor	No evidence of primary tumor	No evidence of primary tumor	No evidence of primary tumor
Tis	Carcinoma in situ, Bowen disease, high-grade squamous interepithelial lesion (HSIL), anal interepithelial neoplasia II-III (AIN II-III)	Carcinoma in situ: intraepithelial or invasion of lamina propria
T1	Tumor 2 cm or less in the greatest dimension	Tumor invades submucosa	Tumor invades lamina propria or submucosa and is no greater than 2 cm in size	Tumor 2 cm or less in greater dimension
			T1a – tumor less than 1 cm in size
			T1b – tumor 1 to 2 cm in size
T2	Tumor more than 2 cm but not more than 5 cm in the greatest dimension	Tumor invades muscularis propria	Tumor invades muscularis propria or is greater than 2 cm in size	Tumor more than 2 cm but not more than 5 cm
T3	Tumor more than 5 cm in the greatest dimension	Tumor invades subserosa or into non-peritonealized perirectal tissues	Tumor invades subserosa or non-peritonealized perirectal tissues	Tumor more than 5 cm but not more than 10 cm
T4	Tumor of any size invades adjacent organ(s), e.g., vagina, urethra, bladder (direct invasion of rectal wall, perianal skin, subcutaneous tissue or the sphincter muscle(s) alone is not classified as T4)	Tumor perforates visceral peritoneum (T4a) and/or directly invades other organs or structures (T4b)	Tumor perforates peritoneum or invades other organs	Tumor more than 10 cm in the greatest dimension
N	Regional lymph nodes
NX	Regional lymph nodes cannot be assessed	Regional lymph nodes cannot be assessed	Regional lymph nodes cannot be assessed	Regional lymph nodes cannot be assessed
N0	No regional lymph nodes metastasis	No regional lymph nodes metastasis	No regional lymph node metastasis	No regional lymph nodes metastasis
N1	Metastasis in perirectal lymph nodes	Metastasis in 1 to 3 regional lymph nodes	Regional lymph node metastasis	Regional lymph node metastasis
		N1a - Metastasis in 1 regional lymph node
		N1b – Metastasis in 2 to 3 regional lymph nodes
		N1c Tumor deposit(s), i.e. satellites, in the subserosa or in non-peritonalized pericolic or perirectal soft tissue without regional lymph node metastasis
N2	Metastasis in unilateral internal iliac and/or inguinal lymph nodes	Metastasis in 4 or more regional lymph nodes
		N2a - metastasis in 4 to 6 more regional lymph nodes
		N2a - metastasis in 7 or more regional lymph nodes
N3	Metastasis in perirectal and inguinal lymph nodes and/or bilateral internal iliac and/or bilateral inguinal lymph nodes
M	Distal metastasis
M0	No distal metastasis	No distal metastasis	No distal metastasis	No distal metastasis
M1	Distal metastasis	Distal metastasis	Distal metastasis	Distal metastasis
		M1a – metastasis confined to one organ
		M1b – metastasis in more than one organ or the peritoneum