SMALL INTESTINE (ICD‐O‐3 ICD‐O C17)

Rules for Classification

The classification applies only to carcinomas. There should be histological confirmation of the disease.

Anatomical Subsites (Fig. 155)

Duodenum (C17.0)
Jejunum (C17.1)
Ileum (C17.2) (excludes ileocaecal valve C18.0)

Note

This classification does not apply to carcinomas of the ampulla of Vater.

Regional Lymph Nodes

The regional lymph nodes for the duodenum are the pancreaticoduodenal, pyloric, hepatic (pericholedochal, cystic, hilar) and superior mesenteric nodes.

The regional lymph nodes for the ileum and jejunum are the mesenteric nodes, including the superior mesenteric nodes, and, for the terminal ileum only, the ileocolic nodes, including the posterior caecal nodes.

Schematic illustration of Anatomical Subsites. — **Fig. 155**

TNM Clinical Classification

T – Primary Tumour

TX	Primary tumour cannot be assessed
T0	No evidence of primary tumour
Tis	Carcinoma in situ
T1	Tumour invades lamina propria, muscularis mucosae or submucosa (Fig. 156)
	T1a	Tumour invades lamina propria or muscularis mucosae
	T1b	Tumour invades submucosa
T2	Tumour invades muscularis propria (Fig. 157)
T3	Tumour invades subserosa or non‐peritonealized perimuscular tissue (mesentery or retroperitoneum*) without perforation of the serosa (Fig. 158)
T4	Tumour perforates visceral peritoneum or directly invades other organs or structures (includes other loops of small intestine, mesentery, or retroperitoneum and abdominal wall by way of serosa; for duodenum only, invasion of pancreas) (Figs. 159, 160, 161)

Photo depicts a Tumour invades lamina propria, muscularis mucosae or submucosa. — **Fig. 156**

Photo depicts a Tumour invades muscularis propria. — **Fig. 157**

Note

* The non‐peritonealized perimuscular tissue is, for jejunum and ileum, part of the mesentery and, for duodenum in areas where serosa is lacking, part of the retroperitoneum.

N – Regional Lymph Nodes

NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Metastasis in 1 to 2 regional lymph nodes
N2	Metastasis in 3 or more regional lymph nodes

Photo depicts a Tumour invades subserosa or non‐peritonealized perimuscular tissue without perforation of the serosa. — **Fig. 158**

Photo depicts a Tumour perforates visceral peritoneum or directly invades other organs or structures. — **Fig. 159**

M – Distant Metastasis

M0	No distant metastasis
M1	Distant metastasis

pTNM Pathological Classification

The pT and pN categories correspond to the T and N categories.

pM1	Distant metastasis microscopically confirmed

Note

pM0 and pMX are not valid categories.

pN0

Histological examination of a regional lymphadenectomy specimen will ordinarily include 6 or more lymph nodes. If the lymph nodes are negative, but the number ordinarily examined is not met, classify as pN0.