IL4 and neoplasm: IL4: ipsilateral level IV lymph node; LVI: lymphovascular invasion; PNI: perineural invasion; ENE: extranodal extension; pT: pathological tumor size; pN: pathological nodal status; adjuvant RT: adjuvant radiotherapy; adjuvant CTRT: adjuvant chemoradiotherapy; pN3b: pathological nodal stage 3b.