Abstract
Lymph node metastasis is the leading factor determining the outcome of mucosal cancer, and the factors associated with lymph node metastasis—and thus with disease outcome—are the depth and invasion patterns of the primary tumor. The General Rules for Clinical and Pathological Studies on Oral Cancer specify clinical growth patterns as the principal method for clinical classification. This method re-categorized oral cancer into superficial, exophytic, and endophytic types because of their universality and reproducibility, based on conventional observation-based classification and on the concept that “classification is possible and useful”. Because a subgroup of lesions in the endophytic group is strongly associated with poor prognosis, this growth pattern-based classification is currently under debate as to whether this subgroup should be reclassified as an independent lesion type with characteristic gross and histological images and pathological features. Because this issue will be addressed by the Scientific Committee's Working Group 1, here I will discuss, as the next-generation method of clinical classification, a novel classification method that reflects tumor invasion patterns.
It is my belief that the current clinical classification method needs to be updated to reflect the patterns of tumor invasion. Owing to advances in surgical pathology, clinical classification of gastrointestinal lesions is performed using silhouette classification. This classification is based on the morphology of the mucosal surface as well as the patterns of tumor invasion. The Yamamoto-Kohama mode of invasion (YK classification), which has been used to determine the degree of malignancy of oral squamous cell carcinoma, is an equivalent version of the silhouette classification and can be used as the next-generation classification method. Macroscopic and imaging evaluation should not be performed with the eyes alone, but should be accompanied by a knowledge base for surgical pathology. Clinical classification should reflect the knowledge accumulated on all types of oral cancer.
