Importance of tumor thickness and depth of invasion in nodal involvement and prognosis of oral squamous cell carcinoma: a review of the literature

BACKGROUND: Oral mucosa squamous cell carcinoma (OSCC) has locoregional evolution, with frequent neck involvement (the most important parameter for prognosis). There are still many doubts concerning the best way to approach N0 neck disease in early-stage lesions (T1 and T2). Many parameters have been studied to identify N0 patients with a high likelihood of harboring occult node metastases or of having them develop. METHODS: A review of the studies analyzing "tumor thickness"/"depth of invasion" in predicting regional metastases and survival was undertaken. RESULTS: The literature suggests that "tumor thickness"/"depth of invasion" is a reliable parameter for predicting regional nodal involvement and survival in OSCC. CONCLUSIONS: Authors are in substantial agreement regarding the reliability of tumor thickness. The lack of comparable study groups, measurement techniques, and cut-off values points to the need for further studies so as to reach a consensus and to develop therapy protocols that include tumor thickness.