268 Chapter 17 invasion”) with associated distortion or destruction of the underlying pulmonary architecture” described in 1997 by Silver and Askin was not incorporated. These descriptions are clearly associated with invasion. However, leaving the fibroplasia out of the definition for 1999 WHO classification turned out to be a catch 22. In hindsight, iatrogenic collapsed AIS also fitted within the description of papillary carcinoma in the 1999 WHO classification and subsequent managerial classifications, the possibility of overdiagnosis as papillary carcinoma (and by definition invasive carcinoma) was created. Aida et al. underscored in 2004 the poor prognosis of papillary carcinoma according to Silver and Askin too and concluded in their paper that the combination of WHO and Silver and Askin criteria (WHO-SA) should be used for prognostic correlation382. However, 10 years after the modified 1999 WHO classification of pulmonary adenocarcinomas the original worse prognosis of papillary carcinoma16 turned to become a favorable prognosis in 381 383 310 384. To understand this prognostic reversal, the distinction between papillary adenocarcinoma and papillary mimics, as described above and in chapter 12 is very important. In the managerial classification of 2012 a new category of “minimally invasive adenocarcinoma”13 was. described. It is worth highlighting that the aforementioned category was not initially recognized in the seminal paper by Noguchi and colleagues, which described adenocarcinoma in-situ and employed stricter invasion criteria10. During the 1999-2010 interval, cases with collapsed AIS or biological collapse were likely overdiagnosed as lepidic invasive adenocarcinoma. Nowadays, pathologists feel that when they use the current WHO classification of pulmonary adenocarcinomas for the assessment of invasion, that they are conscious incompetent. In hindsight 24 years after the 1999 WHO classification the experts of 1999 were probably unconscious incompetent, when they modified the definition of papillary carcinoma. STAS also was introduced as expert opinion in the WHO classification, while in the preparing sessions only half of the pathologists supported the concept. The effect of the incorporation in the WHO resulted in a tsunami on STAS papers. The process of selection and incorporating of various opinions the WHO classification of pulmonary adenocarcinomas leaves room for improvement. Currently, the criteria for a modification in the WHO classification are more scientifically defined. There have to be at least two independent peer reviewed studies performing a properly designed case control study with good statistics. The study in chapter 15 is comparing tumors according to the WHO (control) and to a revised classification (case) with statistically estimated sample size before the start of the study. The reduction of variation in and increase in ‘consensus percentage’ as well as the increase in kappa scores from the control (WHO classification 2021; 0.27) compared to case (Revised classification;0.45-0.62) is the first study at that shines light on the horizon of invasion assessment in pulmonary adenocarcinomas. Despite their current uncertainty, pathologists will become proficient in identifying invasion in pulmonary
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