Abstract
T classification of gingival carcinomas includes the controversial point in T4 criteria. Carcinomas originating in the mucous membrane and invading neighboring tissues can be regarded as T4. Alveolus and gingiva compose a special structure such as bone lines oral mucous membrane just several millimeters below the mucosal surface. Thus some interpretations for T4 criteria are possible in gingival cancer. This paper reports the result of a comparative study on the validity of UICC criteria, Japan Society for Head and Neck Cancer (JSHNC) criteria, level of mandibular canal (LMC) criteria, sinus and nasal floor (SNF) criteria in T classification of gingival cancer. A total of 1187 cases of lower gingival cancers collected in Japan Society for Oral Tumors from 24 clinical centers and 37 cases of upper gingival cancers and hard palate cancers from a single clinical center was analyzed. Data were analyzed with reference to distribution of T-goups, survival rate, multivariate analysis and treatment choice. T classification by UICC criteria did not make sense showing high distribution in T4. JSHNC criteria showed an incomplete revision in T distribution and survival rate. LMC criteria and SNF criteria made great revision. Result of factor analysis by multivariate analysis showed that high coefficient of determination was observed in bone invasion level, tumor size and deep soft tissue invasion of the primary site. Multivariate analysis by mathematical quantification method II revealed that LMC criteria had good factor loading toward T size and well reflects the basic concept of UICC criteria signifying that T-groups are determined by surface tumor size. Analysis of bone invasion mode and bone invasion level in lower gingival carcinomas also showed LMC criteria can offer an adequate guide for treatment choice in mandibular bone surgery. The present several analyses can be summarized by the fact that LMC criteria is the most proper in lower gingival cancer and SMF criteria in upper gingival cancer and hard palate cancer for T classification.
