# Depth of invasion (DOI)

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

## TL;DR

Depth of invasion is how far down a cancer has grown from the surface it started on, measured in millimetres on the pathology slide; in mouth cancer it now sets the T stage and a depth over 4 mm means the neck nodes are treated even when they look clean, and in early stomach cancer it decides whether an endoscopic removal was enough.

## Summary

What is measured: the distance from the reconstructed basement membrane of the adjacent normal mucosa to the deepest point of invasion, measured perpendicular to the surface; unlike tumour thickness it excludes the exophytic part. How: microscopy of the resection or biopsy specimen. Thresholds by site: oral cavity (AJCC 8th edition) 5 mm or less, 5 to 10 and over 10 mm move the T stage, and elective neck dissection is recommended above 3 to 4 mm (the D'Cruz trial of elective against therapeutic neck dissection and the Huang meta-analysis); stomach and oesophagus distinguish mucosal from submucosal invasion (SM1 under 500 micrometres against SM2 and deeper) to judge whether endoscopic submucosal dissection was curative (the eCura system); cervix FIGO 2018 stage IA1 is under 3 mm and IA2 3 to 5 mm; endometrial cancer splits at half the myometrial thickness for the ESGO risk groups and adjuvant brachytherapy; cutaneous squamous cell carcinoma over 6 mm or beyond the subcutaneous fat is high risk (Brigham and Women's T2b); Breslow thickness in melanoma is the analogous measure. What a result changes: T stage, elective treatment of the neck, completion surgery after endoscopic resection, adjuvant radiotherapy and sentinel node thresholds. Where it matters: oral, tongue and buccal cancers, early gastric cancer, advanced cutaneous SCC, NSMP endometrial cancer and early cervical cancer.

## Fields

- Kind: Term
- Last checked: 2026-09-17
- Also known as: DOI; depth of invasion; tumour depth; tumor depth; invasion depth; depth of stromal invasion; submucosal invasion depth; SM1; SM2; T1a versus T1b; myometrial invasion; deep myometrial invasion; thickness versus depth

## Connected records

- terms: [Breslow thickness](https://onco.cc/terms/breslow-thickness/), [Extranodal extension (ENE)](https://onco.cc/terms/extranodal-extension/), [Grade](https://onco.cc/terms/tumour-grade/), [Lymphovascular invasion (LVI)](https://onco.cc/terms/lymphovascular-invasion/), [No specific molecular profile (NSMP) endometrial cancer](https://onco.cc/terms/nsmp/), [Perineural invasion (PNI)](https://onco.cc/terms/perineural-invasion/), [Sentinel node biopsy](https://onco.cc/terms/sentinel-lymph-node-biopsy/)
- technologies: [Endoscopic resection (EMR / ESD)](https://onco.cc/technologies/endoscopic-resection/)
- cancers: [Advanced cutaneous squamous cell carcinoma](https://onco.cc/cancers/advanced-cutaneous-scc/), [Buccal mucosa and gingivobuccal cancer (oral cancer in India)](https://onco.cc/cancers/buccal-mucosa-cancer/), [Early cervical cancer and fertility-sparing surgery](https://onco.cc/cancers/early-cervical-cancer/), [Early gastric cancer](https://onco.cc/cancers/early-gastric-cancer/), [Early hepatocellular carcinoma (BCLC 0 and A)](https://onco.cc/cancers/hcc-early/), [Endometrial cancer with no specific molecular profile](https://onco.cc/cancers/endometrial-nsmp/), [Oral cavity cancer (mouth and tongue)](https://onco.cc/cancers/oral-cavity-cancer/), [Oral tongue and floor of mouth cancer](https://onco.cc/cancers/oral-tongue-cancer/)

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