190 Chapter 6 This study investigated whether MET positivity is associated with LNM (pN+ and occult) in early oral tongue SCC (OTSCC). This association was compared with DOI > 4 mm, a known predictor of occult LNM. We further, hypothesized on the potential added value of MET positivity in the clinical decision-making on END. Materials & Methods Ethics statement Human tissues and patient data were used according to “The Code of Conduct for Responsible Use” and “The Code of Conduct for Health Research” as stated by the Federation of Dutch Medical Scientific Societies (20). Furthermore, The Erasmus MC Medical Ethics Committee approved the research protocol (MEC-2016-751). Study design, patient and tumor characteristics Inclusion criteria were patients with early OTSCC (pT1-2) treated primary with surgery with a neck dissection, at the Leiden University Medical Center (LUMC, between 1995 and 2010) and the Erasmus MC Cancer Institute (Erasmus MC, between 2006 and 2013). All patient and tumor characteristics, except the DOI, were retrieved from the patient files including: gender, age, tumor diameter (cm), TNM (21), extranodal extension (21), and margin status (21, 22). The DOI was measured according to the guidelines of the 8th edition of the AJCC (5). HE sections – made for diagnostic assessment – were retrieved from the archives and scanned using the NanoZoomer 2.0-HT slide scanner (Hamamatsu Photonics, Hamamatsu, Japan). Other tumor characteristics (i.e. degree of differentiation, pattern of invasion, lymphovascular invasion, perineural invasion, and data on postoperative radiotherapy) were not further recorded or analyzed in this study. Follow-up data in respect to OS and DFS were also recorded. A previous history of head and neck cancer was a reason for exclusion. Tissues, antibody and immunohistochemistry Formalin-fixed paraffin-embedded tissue blocks representative of the included cancers were retrieved from the tissue banks of the departments of pathology from both
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