Depth of Invasion
Also written as: DOI — Depth of Invasion
A histopathological measurement indicating how deeply an oral carcinoma penetrates below the mucosal surface, used as a key criterion for T-category staging in the AJCC 8th edition.
Full Definition
Depth of invasion (DOI) is the vertical measurement from the reconstructed mucosal surface to the deepest point of tumour infiltration in oral squamous cell carcinoma. It was incorporated as a staging parameter in the AJCC 8th edition (2017), distinguishing it from tumour thickness, which is measured from the surface of the tumour. DOI directly influences T-category upstaging: ≤5 mm corresponds to T1, >5–10 mm to T2, and >10 mm to T3 irrespective of tumour size. Editors must ensure that authors correctly use 'depth of invasion' (not 'tumour thickness') when referencing AJCC 8th edition criteria, as the two are histologically distinct measurements.
Usage
Usage note: 'Depth of invasion' and 'tumour thickness' are not synonymous. DOI is measured from the reconstructed mucosal basement membrane, not from the surface of an exophytic tumour. Flag manuscripts that conflate the two terms.
In Context
- "The pathology report confirmed a depth of invasion of 7 mm, upstaging the tumour from T1 to T2 per the AJCC 8th edition." — Histopathology report
- "The author wrote 'tumour thickness' when the AJCC 8th edition criterion of 'depth of invasion' was intended; the editor corrected this distinction with a query to the author." — Manuscript editing note