Tumor thickness and risk of lymph node metastasis in patients with squamous cell carcinoma of the tongue

Objectives Oral squamous cell carcinomas, and tongue malignancies in particular, are among the most common tumors of the oral cavity. Classification for therapeutic and prognostic purposes is routinely made using the tumor, node, metastasis (TNM) system; however, current definitions do not include tumor thickness. We therefore aimed to identify variables associated with survival, and to evaluate the correlation between tumor thickness and the occurrence of lymph node metastasis. Patients and methods All patients undergoing radical tumor resection for squamous cell carcinomas of the tongue between 2000 and 2012 were included. Specimens were analyzed histopathologically and co-variables were interpreted. Follow-up was performed clinically and radiologically for at least 3 years according to current guidelines. Results We included 492 patients who had a median follow-up of 70 months. Variables associated with survival (p < 0.05) were age, tumor stage, N stage, UICC (Union for International Cancer Control) stage, tumor grade, and recurrence. In the receiver operating characteristic curve and Youden-Index analyses, the optimal tumor thickness cut-off was 8 mm to detect significant differences in overall survival. Conclusion We highlight the importance of tumor thickness as a predictive variable in tongue cancer. Specifically, a cut-off point of 8 mm allowed for a more accurate and statistically precise prediction of lymph node metastasis. These findings could supplement the current classification of tongue cancers and form the basis for treatment.