Observer variation in the histopathologic assessment of extranodal tumor spread in lymph node metastases in the neck

Background Extranodal spread (ENS) of tumors is widely used as a prognosticator for patients with head and neck cancer and is used as an indicator for postoperative treatment. However, the histopathologic agreement among pathologists on the assessment of the presence or absence of this criterion has never been studied. Methods The interobserver and intraobserver agreement among 10 pathologists on the diagnosis of ENS in 41 tumor-positive lymph nodes was evaluated. Results The kappa value of the interobserver agreement among pathologists varied between 0.14 and 0.75, the overall kappa value was 0.42 and 0.49 in the 2 scoring sessions. The intraobserver kappa value varied between 0.49 and 0.95. Conclusion The intraobserver and interobserver agreement among pathologists in the assessment of the presence of ENS was low in metastatic lymph nodes in the neck. Because of the widely accepted prognostic significance and therapeutic consequences of ENS, there is a need for internationally accepted reproducible criterion for the histopathologic assessment of ENS in metastatic lymph nodes in the neck