A comparative analysis of the significance of depth of invasion and tumor thickness in the staging of oral cavity squamous cell carcinoma.

Objective: According to the American Joint Committee on Cancer (AJCC) 8th edition, tumor depth of invasion is one of the essential parameters required for the staging of oral cavity squamous cell carcinoma (OSCC). We conducted this study to overview our diagnostic challenges and share our institutional experiences related to the measurement of depth of invasion.

Methods: We selected 90 OSCC cases between 2017 and 2023. The depth of invasion and tumor thickness were remeasured in each case, and the tumor stage was assigned according to the AJCC 8th edition criteria.

Results: We found that 84 of 90 (93.3%) had the same tumor stage, whether defined by tumor thickness or depth of invasion. Overall, the difference between tumor thickness and depth of invasion ranged from 0 to 3 mm. In only 6 of the 90 (6.7%) cases was the tumor stage changed based on tumor thickness. Of these 6 cases, 4 were upgraded from T1 to T2, while the remaining 2 were upgraded from T2 to T3.

Conclusions: We observed that in 93.3% of our OSCC cases, tumor stage remained the same with either depth of invasion or tumor thickness, while 6.7% were upstaged based on tumor thickness. Based on the study observations, tumor thickness appears to be more straightforward to measure than depth of invasion. In contrast, depth of invasion measurement requires certain prerequisites and can pose diagnostic challenges. Additional studies with larger cohorts are needed to compare tumor thickness with depth of invasion findings.