Introduction: A histologic grading system for invasive lung adenocarcinoma (ADC) has been proposed by the International Association for the Study of Lung Cancer (IASLC) Pathology Committee in June 2020. This study evaluated the prognostic value of the IASLC histologic grading system (the IASLC system) in a large Japanese cohort.Methods: We performed comprehensive histologic subtyping using the semiquantitative estimation of five major patterns and complex glandular patterns in patients with a completely resected lung ADC and determined the histologic grade using the IASLC system. Concordance index and receiver-operating characteristic curves were used to evaluate the clinical utility of the IASLC system for recurrence and death; the comparison was performed with the architectural-pattern system (the Arch system) and the grading system on the basis of the two most predominant patterns (the Sica's system).Results: Of 1002 patients with invasive ADC, 235 had recurrent disease and 166 died of lung cancer. The concordance index and area under the curve of the IASLC system were 0.777 and 0.807 for recurrence and 0.767 and 0.776 for death, respectively. These were similar to those of the Arch system (0.763 and 0.796 for recurrence, 0.743 and 0.755 for death) and the Sica's system (0.786 and 0.814 for recurrence, 0.762 and 0.773 for death). Conclusions:We reported that the IASLC system for invasive lung ADC has prognostic significance by evaluating a large Japanese cohort. We believe that the IASLC grading system will provide physicians with better information for postsurgery treatment.

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These findings suggest that GATA6 might interact with HNF4α and contribute to the development of mucinous-type LAs.

Our findings show that RNA ISH is useful for detecting ALK rearrangement with high sensitivity and specificity relative to conventional IHC/FISH tests. Thus, RNA ISH, which is an easy and rapid assay, could be an alternative method to IHC and FISH.

Background: Cribriform-predominant adenocarcinoma of the lung (Cribri-ADC) is a recently described tumor growth pattern. However, its prognostic impact has not been clearly determined. We analyzed the data of a series of 1,057 Japanese patients with resected lung adenocarcinoma to identify the clinical significance of Cribri-ADC.Methods: Cribriform pattern (Cribri-p) is defined as invasive back-to-back fused tumor glands with poorly formed glandular spaces or invasive tumor nests comprising tumors cells that produced glandular lumina. We investigated the correlations of Cribri-p and Cribri-ADC with clinicopathological factors as well as diseasefree survival (DFS) and overall survival (OS).Results: Cribri-p was present in 217 patients (20.5%) and Cribri-ADC was determined in 25 patients (2.4%). Cribri-p was associated with larger tumor size, pleural invasion, vascular invasion, lymphatic invasion, and spreading through air spaces (STAS) (all, P<0.0001). Cribri-ADC was associated with younger age (P=0.019), vascular invasion (P=0.0025), STAS (P<0.0001), and ALK rearrangement (P=0.012). The DFS curve of patients with Cribri-ADC was identical to that of patients with solid adenocarcinoma; however, the OS curve was located between that of patients with papillary and acinar adenocarcinoma. Of the 10 patients who had tumor recurrences, eight had EGFR mutations or ALK rearrangement, six of whom achieved relatively long survival (median, 64.6, range, 37.4-113 months) following treatment with tyrosine kinase inhibitors (TKIs). In multivariate analysis, Cribri-ADC was not an independent prognostic factor of either recurrence or death.Conclusions: Cribri-ADC is associated with a higher risk of recurrence; however, most patients can be successfully treated with TKIs.