STOMACH (ICD‐O‐3 C16)

Rules for Classification

The classification applies only to carcinomas. There should be histological confirmation of the disease. Cancers involving the oesophagogastric junction whose epicentre is within the proximal 2 cm of the cardia (Siewert types I/II) are to be staged as oesophageal cancers. Cancers whose epicentre is more than 2 cm distal from the oesophagogastric junction will be staged using the Stomach Cancer TNM and Stage even if the oesophagogastric junction is involved.

Anatomical Subsites (Fig. 142)

Fundus (C16.1)
Corpus (C16.2)
Antrum (C16.3) and pylorus (C16.4)

Regional Lymph Nodes (Figs. 143, 144)

The regional lymph nodes of the stomach are the perigastric nodes along the lesser (1, 3, 5) and greater (2, 4a, 4b, 6) curvatures, the nodes along the left gastric (7), common hepatic (8), splenic (11) and coeliac arteries (9), and the hepatoduodenal nodes (12).

Involvement of other intra‐abdominal lymph nodes such as retropancreatic, mesenteric and para‐aortic is classified as distant metastasis.

TNM Clinical Classification

T – Primary Tumour

TX	Primary tumour cannot be assessed
T0	No evidence of primary tumour
Tis	Carcinoma in situ: intraepithelial tumour without invasion of the lamina propria, high‐grade dysplasia
T1	Tumour invades lamina propria, muscularis mucosae or submucosa (Fig. 145)
T1a	Tumour invades lamina propria or muscularis mucosae
T1b	Tumour invades submucosa
T2	Tumour invades muscularis propria (Fig. 145)
T3	Tumour invades subserosa (Figs. 145, 146, 147)
T4	Tumour perforates serosa (visceral peritoneum) or invades adjacent structures^1,2,3
	T4a	Tumour perforates serosa
	T4b	Tumour invades adjacent structures^{2, 3} (Fig. 148)

Schematic illustration of Anatomical Subsites. — **Fig. 142**

Schematic illustration of Regional Lymph Nodes. — **Fig. 143**

Photo depicts a Tumour invades lamina propria, muscularis mucosae or submucosa. — **Fig. 145**

Photo depicts a Tumour invades subserosa. — **Fig. 146**

Schematic illustration of tumour invades subserosa. — **Fig. 147**

Notes

1 The adjacent structures of the stomach are the spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal gland, kidney, small intestine and retroperitoneum.

2 Intramural extension to the duodenum or oesophagus is classified by the depth of greatest invasion in any of these sites including the stomach (Figs. 147, 149).

3 Tumour that extends into gastrocolic or gastrohepatic ligaments or into greater or lesser omentum, without perforation of visceral peritoneum, is T3 (Fig. 150).

Photo depicts a Tumour invades adjacent structures. — **Fig. 148**

Schematic illustration of Intramural extension to the duodenum or oesophagus is classified by the depth of greatest invasion in any of these sites including the stomach. — **Fig. 149**

Photo depicts a Tumour that extends into gastrocolic or gastrohepatic ligaments or into greater or lesser omentum, without perforation of visceral peritoneum, is T3. — **Fig. 150**

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 (Fig. 151)
N2	Metastasis in 3 to 6 regional lymph nodes (Fig. 152)
N3	Metastasis in 7 or more regional lymph nodes
	N3a	Metastasis in 7 to 15 regional lymph nodes (Fig. 153)
	N3b	Metastasis in 16 or more regional lymph nodes (Fig. 154)

M – Distant Metastasis

M0	No distant metastasis
M1	Distant metastasis (Fig. 154)

Note

Distant metastasis includes peritoneal seeding, positive peritoneal cytology, and omental tumour not part of continuous extension.

pTNM Pathological Classification

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

pM1	Distant metastasis microscopically confirmed
pN0	Histological examination of a regional lymphadenectomy specimen will ordinarily include 16 or more lymph nodes. If the lymph nodes are negative, but the number ordinarily examined is not met, classify as pN0

Note

pM0 and pMX are not valid categories.