Examination of the relationship between the tumor thickness and lymph node metastasis in superficial pharyngeal cancer and indication for local resection.

【background】In recent years, superficial pharyngeal cancer (PC) have been treated with endoscopic resection widely. Tumor diameter is used to evaluate the primary lesion in the TMN classification of PC. However, the relationship between tumor diameter and lymph node (LN) metastasis is still not clear.【Subjects】Between January 2010 and December 2020, 296 PC cases were initially treated endoscopically. We retrospectively evaluated the relationship between T stage according to TNM classification and the ratio of LN metastasis. And we also evaluated the relationship between tumor thickness and the ratio of LN metastasis. In this study, we divided tumor thickness ＜1000μm (group A) and tumor thickness≧1000μm (group B).【Result】Of all 296 cases, 17 case had LN metastasis, and all had cervical LN metastases. According to the TMN classification, Tis, T1, T2, T3 has 104, 75, 87, 30 lesions respectively, and the cases of LN metastasis were 0 for Tis, 4 for T1 (5.3%), 9 for T2 (10.3%), and 4 for T3 (13.3%) (p = 0.343). According to the Tumor thickness classification, group A and group B has 130 and 62 lesions respectively, and the cases with LN metastasis were 2 (1.5%) with group A and 15 (24.2%) with group B (p <0.001).【Conclusion】For stratification of the risk of LN metastasis of superficial PC,  tumor thickness was considered to be more useful than tumor diameter (TNM classification).