Defining Morphologic Features of Invasion in Pulmonary Nonmucinous Adenocarcinoma With Lepidic Growth: A Proposal by the International Association for the Study of Lung Cancer Pathology Committee

Erik Thunnissen*, Mary Beth Beasley, Alain Borczuk, Sanja Dacic, Keith M. Kerr, Birgit Lissenberg-Witte, Yuko Minami, Andrew G. Nicholson, Masayuki Noguchi, Lynette Sholl, Ming-Sound Tsao, John le Quesne, Anja C. Roden, Jin-Haeng Chung, Akihiko Yoshida, Andre L. Moreira, Sylvie Lantuejoul, Giuseppe Pelosi, Claudia Poleri, David HwangDeepali Jain, William D. Travis, Elisabeth Brambilla, Invasion Working Group, Gang Chen, Johan Botling, Lukas Bubendorf, Mari Mino-Kenudson, Noriko Motoi, Teh Ying Chou, Mauro Papotti, Yasushi Yatabe, Wendy Cooper

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Introduction: Since the eight edition of the Union for International Cancer Control and American Joint Committee on Cancer TNM classification system, the primary tumor pT stage is determined on the basis of presence and size of the invasive components. The aim of this study was to identify histologic features in tumors with lepidic growth pattern which may be used to establish criteria for distinguishing invasive from noninvasive areas. Methods: A Delphi approach was used with two rounds of blinded anonymized analysis of resected nonmucinous lung adenocarcinoma cases with presumed invasive and noninvasive components, followed by one round of reviewer de-anonymized and unblinded review of cases with known outcomes. A digital pathology platform was used for measuring total tumor size and invasive tumor size. Results: The mean coefficient of variation for measuring total tumor size and tumor invasive size was 6.9% (range: 1.7%–22.3%) and 54% (range: 14.7%–155%), respectively, with substantial variations in interpretation of the size and location of invasion among pathologists. Following the presentation of the results and further discussion among members at large of the International Association for the Study of Lung Cancer Pathology Committee, extensive epithelial proliferation (EEP) in areas of collapsed lepidic growth pattern is recognized as a feature likely to be associated with invasive growth. The EEP is characterized by multilayered luminal epithelial cell growth, usually with high-grade cytologic features in several alveolar spaces. Conclusions: Collapsed alveoli and transition zones with EEP were identified by the Delphi process as morphologic features that were a source of interobserver variability. Definition criteria for collapse and EEP are proposed to improve reproducibility of invasion measurement.
Original languageEnglish
Pages (from-to)447-462
Number of pages16
JournalJournal of Thoracic Oncology
Issue number4
Early online date2023
Publication statusPublished - Apr 2023

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