Figure 5: Extent of selective neck dissection in clinical N0 neck. a) For cancers of the oral cavity it is level I–III that has to be dissection, while for cancers of the tongue levels I–IV must be considered, b) For oropharyngeal cancers it is level II–III, c) For glottic and supraglottic cancers of the larynx it is level IIA–III, d) For hypopharyngeal cancers it is level IIA–IV.