Interobserver agreement between pathologist, pulmonologist and molecular pathologist to estimate the tumour burden in rapid on-site evaluation smears from endosonography and guided bronchoscopy

Objective: A growing number of studies have suggested that non-pathologists can reliably assess the adequacy and malignancy in rapid on-site evaluation (ROSE) smears prepared during endoscopic sampling procedures. However, no study has verified whether they can also consistently estimate the tumour burden, which is critical for the molecular profiling of lung cancer. We aimed to assess the interobserver agreement (IOA) between a pathologist, a pulmonologist (previously trained in lung and lymph node cytopathology) and a molecular pathologist for the tumour burden in ROSE smears. Methods: The ROSE smears of consecutive patients with suspected lung cancer undergoing endosonography or guided bronchoscopy were assessed independently by a pathologist, a pulmonologist and a molecular pathologist (gold standard). The IOA for the tumour burden, assessed through k-statistics, was the primary outcome. Results: A total of 322 ROSE smears obtained from 162 patients were evaluated. The IOA between the molecular pathologist and pulmonologist was very good (moderate to substantial), although slightly inferior to the IOA between the molecular pathologist and pathologist in the whole slide set (k: 0.707, 95% confidence interval [CI]: 0.677-0.739 vs 0.793, 95% CI: 0.762-0.815), as well as in smears prepared from lymphadenopathy (k: 0.783, 95% CI: 0.760-0.855 vs 0.827, 95% CI: 0.728-0.892) or from pulmonary nodules/masses (k: 0.558, 95% CI: 0.416-0.686 vs 0.715, 95% CI: 0.621-0.767). Conclusions: A professionally trained pulmonologist can reliably estimate the tumour burden in bronchoscopically derived ROSE smears, especially in the setting of lymphadenopathy. This can be particularly useful in institutions where a cytopathologist is not available regularly.