Stomach cancer staging
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Fahad Hasan, M.D.[2] Parminder Dhingra, M.D. [3] Mohammed Abdelwahed M.D[4]
Overview
Gastric adenocarcinoma is staged with the tumor–node–metastasis (TNM) system maintained jointly by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC). The current standard is the AJCC 8th edition, implemented January 1, 2018. It is the version used in the NCCN Gastric Cancer Guidelines.[1][2]
The 8th edition uses the same T, N, and M definitions in every setting. It provides three separate stage-grouping schemata for different points in care:
- clinical (cTNM), before treatment
- pathological (pTNM), after upfront resection
- post-neoadjuvant pathological (ypTNM), after preoperative therapy and resection[3][4]
Stage determines the main treatment choice: endoscopic resection, surgery alone, perioperative multimodality therapy, or palliative systemic therapy. Stage is also the strongest determinant of prognosis.[5]
Staging
Anatomic Scope: Esophagogastric Junction Site Rule
Tumors involving the esophagogastric junction (EGJ) are assigned to a staging system by the location of their epicenter:[1][6][7]
- Epicenter ≤2 cm into the proximal stomach (Siewert I–II) is staged as esophageal adenocarcinoma.
- Epicenter >2 cm into the stomach (Siewert III) is staged as gastric cancer.
- Cardia tumors that do not involve the EGJ are also staged as gastric cancer.
- This changed from the 7th edition, under which Siewert III tumors were staged as esophageal.
Siewert category should therefore be assigned for every proximal tumor before staging. EGJ adenocarcinomas staged by the esophageal schema use pathological stage groups that also incorporate histologic grade.[8]
TNM Definitions (AJCC 8th Edition)
| Category | Definition |
|---|---|
| TX | Primary tumor cannot be assessed |
| T0 | No evidence of primary tumor |
| Tis | Carcinoma in situ: intraepithelial tumor without invasion of the lamina propria; high-grade dysplasia |
| T1a | Invades lamina propria or muscularis mucosae |
| T1b | Invades submucosa |
| T2 | Invades muscularis propria |
| T3 | Penetrates subserosal connective tissue without invasion of the visceral peritoneum or adjacent structures |
| T4a | Invades serosa (visceral peritoneum) |
| T4b | Invades adjacent structures or organs |
| Category | Definition |
|---|---|
| NX | Regional nodes cannot be assessed |
| N0 | No regional lymph node metastasis |
| N1 | 1–2 positive regional nodes |
| N2 | 3–6 positive regional nodes |
| N3a | 7–15 positive regional nodes |
| N3b | ≥16 positive regional nodes |
| Category | Definition |
|---|---|
| M0 | No distant metastasis |
| M1 | Distant metastasis, including positive peritoneal cytology |
| GX | Grade cannot be assessed |
| G1 / G2 / G3 | Well / moderately / poorly differentiated or undifferentiated (grade is recorded but not used in gastric stage grouping) |
Key classification rules[2]
- Extension into the gastrocolic or gastrohepatic ligament, or into the greater or lesser omentum, is T3 if the overlying visceral peritoneum is intact. It is T4 if that peritoneum is perforated.
- Adjacent structures (T4b) include the spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal gland, kidney, small intestine, and retroperitoneum.
- Intramural extension into the duodenum or esophagus is not invasion of an adjacent structure. It is classified by the greatest depth of invasion at any site.
Stage Groupings
The same TNM combination can map to different stage groups depending on the schema. For example, T2N0 is clinical stage I, pathological stage IB, and post-neoadjuvant stage I. Always document the prefix (c, p, or yp) and use the matching table.[7][3]
Clinical Stage (cTNM): Before Treatment
Clinical stage groups are deliberately simplified relative to the pathological groups.[3][2]
| cT \ cN | cN0 | cN1–N3 |
|---|---|---|
| Tis | 0 | — |
| T1 | I | IIA |
| T2 | I | IIA |
| T3 | IIB | III |
| T4a | IIB | III |
| T4b | IVA | IVA |
| Any T, any N, M1 | IVB | |
Pathological Stage (pTNM): After Upfront Resection
The pathological groups incorporate the N3a/N3b split.[2][1]
| pT \ pN | N0 | N1 | N2 | N3a | N3b |
|---|---|---|---|---|---|
| Tis | 0 | — | — | — | — |
| T1 | IA | IB | IIA | IIB | IIIB |
| T2 | IB | IIA | IIB | IIIA | IIIB |
| T3 | IIA | IIB | IIIA | IIIB | IIIC |
| T4a | IIB | IIIA | IIIA | IIIB | IIIC |
| T4b | IIIA | IIIB | IIIB | IIIC | IIIC |
| Any T, any N, M1 | IV | ||||
Post-neoadjuvant Pathological Stage (ypTNM): After Preoperative Therapy and Resection
This schema has three non-metastatic stages plus stage IV, and it is distinct from pTNM.[2][3]
| ypT \ ypN | N0 | N1 | N2 | N3 |
|---|---|---|---|---|
| T1 | I | I | II | II |
| T2 | I | II | II | III |
| T3 | II | II | III | III |
| T4a | II | III | III | III |
| T4b | III | III | III | III |
| Any T, any N, M1 | IV | |||
Staging Workup
Staging proceeds sequentially. The aims are to identify patients curable by endoscopic or surgical resection and to exclude occult metastatic disease. The modalities are complementary: EUS assesses depth, CT assesses distant disease, PET/CT detects occult metastases, and laparoscopy evaluates the peritoneum.[5][2]
| Modality | Role | Performance and limitations |
|---|---|---|
| EGD with biopsy | Establishes the diagnosis, tumor location, relationship to the EGJ, and Siewert category. Obtain 6–8 biopsies of suspicious or ulcerated lesions.[2] | Defines the anatomic scope; does not stage depth. |
| CT chest/abdomen/pelvis (IV ± oral contrast) | Baseline study for locoregional extent and distant metastasis. | T-staging accuracy ~77–89%; N-staging ~69–92%. Sensitivity for peritoneal disease is only ~25–50%.[5] |
| Endoscopic ultrasound (± FNA) | Most accurate locoregional (T/N) modality. Recommended before treatment, especially when early vs. locally advanced disease will change management. | Distinguishes T1–T2 from T3–T4 with sensitivity ~86% and specificity ~91%. N-staging is weaker (sensitivity ~69%, specificity ~84%) and is improved by FNA of suspicious nodes. Cannot reliably separate superficial from deep submucosal invasion.[9][5] |
| Endoscopic resection (EMR/ESD) | Required for accurate T1 substaging: superficial pT1b ≤500 µm vs. deep pT1b >500 µm. May also be therapeutic in selected early lesions. | Definitive staging step for suspected T1a/T1b disease.[2] |
| FDG-PET/CT | For locally advanced disease or equivocal CT findings. | More sensitive than CT for distant metastases (up to ~74% vs. 47–59%). Insensitive for diffuse or mucinous (poorly FDG-avid) tumors and poor for peritoneal disease.[5][10] |
| Staging laparoscopy with peritoneal washings | Recommended for potentially resectable M0 disease that is ≥cT3 and/or node-positive. | Detects radiographically occult peritoneal or liver metastases in ~18–30% of CT-"resectable" patients. Positive cytology is M1 even without visible implants.[5][2][10] |
Nodal yield: A reliable pN or ypN category, including a valid N3a/N3b distinction, requires an adequate lymphadenectomy. Generally ≥16 nodes should be examined, consistent with D2 dissection. Inadequate yield causes understaging and stage migration (the "Will Rogers" effect).[2][11]
Stage and Prognosis
- Localized (stage I) disease: 5-year relative survival is ~75% with treatment. Early lesions are curable by endoscopic or surgical resection.[5]
- Locally advanced (stage II–III) disease: 5-year overall survival is ~45% with perioperative therapy plus surgery.[5]
- Metastatic (stage IV) disease: 5-year survival is <10%.[5]
- Validation: The 8th edition produces ordered, well-separated survival curves in Eastern and Western cohorts. Reported concordance indices are ~0.80 for clinical, ~0.72 for pathological, and ~0.80 for post-neoadjuvant schemata.[12][3][13]
Changes from the AJCC 7th Edition
- New schemata: Separate clinical (cTNM) and post-neoadjuvant (ypTNM) stage groups were introduced for the first time. This reflects routine use of neoadjuvant and perioperative therapy.[3][7]
- N3a/N3b now affect stage grouping: These subcategories existed in the 7th edition but were not used for grouping.[14]
- Stage III migration:
- EGJ site rule: Siewert III tumors are now staged as gastric.[6]
- Peritoneal cytology: Positive peritoneal cytology is formally classified as M1 (stage IV).[6][10]
Limitations and Areas of Uncertainty
- ypTNM accuracy is contested. The AJCC ypTNM was derived from patients largely treated with less-than-D2 lymphadenectomy. It collapses non-metastatic disease into three stages and does not capture tumor regression. Several modified ypTNM systems outperform it prognostically.[15][16][17]
- ypT0 tumors are unclassifiable. ypT0N0 and ypT0N+ disease (complete or near-complete primary response) has no AJCC ypTNM stage, despite being a distinct and often favorable group.[15]
- Clinical understaging is common. Clinical-to-pathological concordance is only ~60%, and understaging predominates, especially for cN. This can lead to omission of beneficial neoadjuvant therapy.[18]
- Restaging CT after neoadjuvant therapy is unreliable. In a population-based cohort, CT stage after neoadjuvant chemotherapy agreed with ypTNM in only 24% of patients (Cohen κ 0.06). Final stage is pathological.[19]
- Alternative nodal metrics. Lymph node ratio and regression-grade–based systems may improve on absolute node counts, particularly within N3b and node-negative disease. They are not incorporated into AJCC staging.[20][21]
- No biomarkers in anatomic staging. HER2, MSI/MMR, PD-L1, and CLDN18.2 status are central to treatment selection but are not part of TNM stage.[4][7]
Clinical Pearls and Common Pitfalls
- Use the correct schema. Do not apply pathological stage groups to clinical TNM; for example, cT2N0 is clinical stage I, not IB.
- N is a node count, not node size: N1 = 1–2, N2 = 3–6, N3a = 7–15, N3b = ≥16 positive nodes.
- Do not omit staging laparoscopy in CT-"resectable" ≥cT3 or node-positive patients. Treat positive cytology as stage IV.
- Retrieve and examine ≥16 nodes for a valid pN or ypN category.
- Stage EGJ tumors by the epicenter rule. Do not stage a Siewert III tumor with the esophageal system.
- Do not equate ypTNM with pTNM prognosis. Stage for stage, post-neoadjuvant patients have worse outcomes, and the AJCC ypTNM has limited discrimination.[15][2]
References
- ↑ 1.0 1.1 1.2 1.3 Amin MB, Edge SB, Greene FL, et al. (eds.) (2017). AJCC Cancer Staging Manual (8th ed.). New York: Springer.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Gastric Cancer. Version 4.2026. NCCN Gastric Cancer Guidelines
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 In H, Ravetch E, Langdon-Embry M, Palis B, Ajani JA, Hofstetter WL, Kelsen DP, Sano T (2018). "The newly proposed clinical and post-neoadjuvant treatment staging classifications for gastric adenocarcinoma for the American Joint Committee on Cancer (AJCC) staging". Gastric Cancer. 21 (1): 1–9. doi:10.1007/s10120-017-0765-y. PMID 28948368.
- ↑ 4.0 4.1 Hirata Y, Noorani A, Song S, Wang L, Ajani JA (2023). "Early stage gastric adenocarcinoma: clinical and molecular landscapes". Nat Rev Clin Oncol. 20 (7): 453–469. doi:10.1038/s41571-023-00767-w.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Patel AK, Sethi NS, Park H (2026). "Gastric Cancer: A Review". JAMA. 335 (5): 439–450. doi:10.1001/jama.2025.20034. PMID 41499132 Check
|pmid=value (help). - ↑ 6.0 6.1 6.2 6.3 Ajani JA, Lee J, Sano T, Janjigian YY, Fan D, Song S (2017). "Gastric adenocarcinoma". Nat Rev Dis Primers. 3: 17036. doi:10.1038/nrdp.2017.36. PMID 28569272.
- ↑ 7.0 7.1 7.2 7.3 Kumagai K, Sano T. Review of the AJCC/UICC 8th-edition TNM staging system for gastric cancer. Jpn J Clin Oncol. 2021.
- ↑ National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Esophageal and Esophagogastric Junction Cancers. Staging tables (ST-3). 2026. NCCN Esophageal and EGJ Cancers Guidelines
- ↑ Evans JA, Chandrasekhara V, Chathadi KV, Decker GA, Early DS, Fisher DA, Foley K, Hwang JH, Jue TL, Lightdale JR, Pasha SF, Sharaf R, Shergill AK, Cash BD, DeWitt JM; ASGE Standards of Practice Committee (2015). "The role of endoscopy in the management of premalignant and malignant conditions of the stomach". Gastrointest Endosc. 82 (1): 1–8. doi:10.1016/j.gie.2015.03.1967. PMID 25935705.
- ↑ 10.0 10.1 10.2 Sundar R, Nakayama I, Markar SR, Shitara K, van Laarhoven HWM; et al. (2025). "Gastric cancer". Lancet. doi:10.1016/S0140-6736(25)00052-2.
- ↑ Son T, et al. J Surg Oncol. 2019.
- ↑ 12.0 12.1 In H, Solsky I, Palis B, Langdon-Embry M, Ajani J, Sano T (2017). "Validation of the 8th Edition of the AJCC TNM Staging System for Gastric Cancer using the National Cancer Database". Ann Surg Oncol. 24 (12): 3683–3691. doi:10.1245/s10434-017-6078-x. PMID 28895113.
- ↑ Bando E, et al. Validation of the AJCC 8th-edition gastric cancer staging system. Gastric Cancer. 2019.
- ↑ 14.0 14.1 Lu J; et al. (2017). "Validation of the American Joint Commission on Cancer (8th edition) changes for patients with stage III gastric cancer: survival analysis of a large series from a Specialized Eastern Center". Cancer Med. 6 (10): 2179–2187. doi:10.1002/cam4.1118. PMID 28913982.
- ↑ 15.0 15.1 15.2 Lin JX; et al. (2019). "Development and validation of a staging system for gastric adenocarcinoma after neoadjuvant chemotherapy and gastrectomy with D2 lymphadenectomy". Br J Surg. 106 (9): 1187–.
- ↑ Zhong Q, et al. Modified ypTNM staging for gastric cancer after neoadjuvant therapy. The Oncologist. 2021.
- ↑ Du et al. PLoS One. 2024.
- ↑ Janczewski et al. J Surg Oncol. 2023.
- ↑ Sandø AD, Fougner R, Grønbech JE, Bringeland EA (2021). "The value of restaging CT following neoadjuvant chemotherapy for resectable gastric cancer. A population-based study". World J Surg Oncol. 19 (1): 212. doi:10.1186/s12957-021-02313-3.
- ↑ Huang et al. Eur J Surg Oncol. 2018.
- ↑ Lin et al. Cancer Med. 2019.