Feasibility of the new TNM classification on the evaluation of progression degree of tongue squamous cell carcinomas

Abstract

The UICC TNM classification is based on criteria for evaluating the progress of oral cancer, and it was revised to the 8th edition in 2016. The depth of invasion （DOI） in T classification and the extra nodal extension （ENE） in N classification were newly introduced. In this study, 107 tongue squamous cell carcinoma cases who underwent surgery in our department were evaluated for TNM classification according to the 7th and 8th editions. We examined the relationship between TNM classification revision, cervical lymph node metastasis and survival rate.
There were cT classification changes due to the revision of the TNM classification in 17 cases （15.9％） and pT classification changes in 6 cases （5.6％）. The number of cases of cervical lymph node metastasis decreased in cT1 and pT1, and increased in cT2 and pT2. Two cases of cT4a and pT4a in the 7th edition were classified into cT3 and pT3 in the 8th edition, so the survival rate of cT3 and pT3 in the 8th edition was lower than in the 7th edition. Three cases of pN2b in the 7th edition were classified as pN3b in the 8th edition, and 3 cases were unhappy outcomes.
This review of the TNM classification of our tongue squamous cell carcinoma cases from the 7th edition to the 8th edition led mainly to the rise of stage. The 8th edition TNM classification faithfully reflects the progress in cervical lymph node metastasis and survival rate, and is considered to be practical.