Table 3.

Advantages and disadvantages of radiological and pathological assessments of ENE

	Radiological assessment	Pathological assessment
1. Patient selection	Performed in all patients, irrespective of age, coexisting morbidity, cancer stage or treatment	Performed in surgical candidates with operable disease
2. Nodal coverage	All nodes/nodal groups	Variability in the amount of tissue available and the number of nodes sampled
3. Technique	Variability in imaging modalities and protocols, including slice thickness	Variability in slide preparation for histological assessment, including slice thickness and orientation
4. Selection of nodes for ENE assessment	Variability in the selection of nodes: all nodes, largest node or node with the most extensive iENE	Variability in the selection of nodes: all nodes, largest node or node with the most extensive pENE
5. Analysis	Multiplanar reconstruction of any node	Confined to the plane and node/amount of the node in the prepared sample
6. Criteria/grades of ENE	Variability in the selection criteria: single criterion, two or more criteria, combinations of criteria, likelihood scores and observer impression. Criteria diluted by non-iENE criteria such as necrosis	Variability in the selection criteria: microscopic versus macroscopic, direct measurements or grading one criterion, two or more criteria and combinations of criteria
7. Observer variation	Intra- and inter-observer variation	Intra- and inter-observer variation
8. Review of data source	Review of images is readily available within and across centres	Review of histology samples may not be readily available, especially across centres and for large sample sizes; therefore, studies frequently rely on retrospective reviews of reports
9. Radiological–pathological correlation	1.Wide variations: node-by-node; nodal-group-by-nodal-group, unilateral-neck-by-unilateral-neck, neck-by-neck 2.Delay between imaging and surgery (>8 weeks) may lead to the progression of ENE

ENE, extranodal extension; iENE, imaging extranodal extension; pENE, pathological extranodal extension.