# Siewert classification (GEJ tumours)

Source: https://onco.cc/terms/siewert-classification/  
OnCo record `siewert-classification` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A way of classifying cancers at the junction of the oesophagus and stomach by where their centre sits, which decides whether they are treated as oesophageal or gastric.

## Summary

The Siewert classification sorts adenocarcinomas of the gastro-oesophageal junction by where the centre of the tumour lies relative to the junction, which decides whether the cancer is managed as oesophageal or gastric. Type I tumours, centred 1 to 5 cm above the junction, are treated as oesophageal adenocarcinoma with regimens such as CROSS or FLOT. Type II tumours, from 1 cm above to 2 cm below, may be treated either way, and type III tumours, 2 to 5 cm below, are treated as gastric cancer with perioperative FLOT with or without durvalumab. The distinction matters for trial eligibility and surgical approach. Readers meet it in the gastric and oesophageal cancer records and in the term contrasting squamous cell carcinoma with adenocarcinoma of the oesophagus.

## Fields

- Kind: Term
- Last checked: 2026-09-07

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Siewert_classification
- Wikipedia: https://en.wikipedia.org/wiki/Siewert_classification

## Connected records

- cancers: [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/), [Oesophageal cancer](https://onco.cc/cancers/esophageal/)
- terms: [Squamous cell carcinoma vs adenocarcinoma of the oesophagus](https://onco.cc/terms/escc-vs-eac/)

---
JSON: https://onco.cc/api/v1/entities/siewert-classification.json