Koos Boeve

47 8th TNM classification prognostic value in oral cancer In this study, the mucosal surface was used instead of the basement membrane. Healthy epithelial thicknesses are approximately 216 µm (SD 59 µm) for the tongue and 99 µm (SD 22 µm) for the mucosa of the anterior floor of the mouth [14]. Because of these small differences between healthy mucosal surfaces and basement membranes, it is improbable that tumour infiltration depth assessment by use of the basement membrane would have a large impact on our data. This was confirmed by an earlier study reporting an extremely high correlation between both methods (3.7% pT category difference) [4]. Another study reported a 5.7% difference in pT category when it compared both methods without correcting for exophytic growth [15]. In cases of metastasis in lymph nodes, all cases with extension of the metastasis through the fibrous capsule into the surrounding tissue should be scored as ENE positive [2]. To study the effect of ENE size in the future, Lydiatt et al. advocate to divide ENE positive lymph nodes with minor ENE (<2 mm) and major ENE (>2 mm and metastasis without recognisable lymph node) [2]. This study demonstrates, in a well-defined retrospective cohort of 211 pT1-T2 (7 th edition) OSCC patients, that the addition of tumour infiltration depth and ENE, as used in the 8 th edition of the AJCC pathological TNM classification, identifies a group of restaged patients with a worse prognosis.