Oral Cavity Cancer: Depth of Invasion (DOI) AJCC 8th ed. 2017

• Distance from adjacent normal basement membrane to deepest point of cancer (Blue plumb lines)
• Correlates with prognosis and occult nodal metastases
• Preoperative assessment
  • Palpation +/- imaging
  • Must distinguish exophytic from invasive cancers (see adjacent figures)

• T-stage increases with every 5mm
  • T1: Less invasive (≤5 mm)
  • T2: Moderate depth (>5 to ≤10mm)
  • T3: Deeply invasive (>10 mm)

• Extrinsic muscle infiltration no longer a staging criterion for T4 because
  • Superseded by DOI
  • Limited extrinsic muscle invasion difficult to assess

Index: Clinical Practice Guidelines for Oral Cancer

Resource Appropriate Oral Cancer Guideline Scenarios