Revisiting the role of depth of invasion in clinical TNM staging.

AJCC 8th Edition of Cancer Staging Manual has now incorporated depth of invasion (DOI) into the clinical staging of oral cavity carcinoma. This inclusion finds relevance as it opens the concept of 3rd dimension in clinical staging. Though a very thoughtful and necessary addendum into the cancer staging, its relevance and prognostic role has been challenged by recent studies. However, there is ambiguity on clinical evaluation of DOI, which has been undermining its relevance in clinical staging. We believe that the subsequent changes to the clinical staging should relook at the concept of 3rd dimension and not DOI for better reliability and acceptance.