Interobserver reproducibility study of the histological patterns of primary lung adenocarcinoma with emphasis on a more complex glandular pattern distinct from the typical acinar pattern.

The newly proposed International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) classification of lung adenocarcinoma has emphasized the prognostic significance of histological subtyping. In this study, 2 surgical pathologists reevaluated 49 consecutive cases of invasive primary pulmonary adenocarcinomas; histological subtyping was performed according to the IASLC/ATS/ERS classification. The 2 reviewers agreed on the predominant pattern in 23 out of 32 independently reviewed cases (71.9%, k = 0.628, 95% confidence interval = 0.442-0.815). Postconsensus, a complex glandular pattern consisting of fused, closely packed glands and cribriform architecture was identified in 9 of 49 (18%) cases. This pattern has a strong association with lymphovascular invasion (78%; P = .0091), high mitotic activity (89%), and higher tumor stage (78%). Frequent association of complex glandular pattern with poor prognostic factors and its overlap with acinar pattern warrant a more detailed description of this pattern in the classification system and a large-scale study to evaluate its prognostic significance.