At the 2023 World Conference on Lung Cancer (WCLC), Dr. Xie Huikang from Shanghai Pulmonary Hospital presented a study titled ” The Value of Lepidic and Invasion Pattern NEW Diagnostic Criteria for the Differential Diagnosis of AIS, MIA from Invasive Adenocarcinoma .” The study aimed to explore whether the new IASLC definitions and standards had an impact on the diagnosis of AIS, MIA, and IAC compared to previous criteria.
MA20.03: The Value of Lepidic and Invasion Pattern NEW Diagnostic Criteria for the Differential Diagnosis of AIS, MIA from Invasive Adenocarcinoma
Background:
The diagnosis of lepidic and invasion pattern has been controversial in some cases. One of the more important implications is the differential diagnosis of adenocarcinoma in situ(AIS), minimally invasive adenocarcinoma(MIA) from invasive adenocarcinoma, because even a small difference in diagnosis between lepidic and invasion pattern can make a huge difference in final diagnosis. Since AIS and MIA have a completely good prognosis, accurate diagnosis has a great impact on the prognostic expectation of patients. In 2022, the IASLC Pathology Committee Invasion working group proposed its own new approach to the controversial distinction between lepidic and invasion pattern. We rediagnosed lung adenocarcinoma in our hospital according to the proposal criteria to determine the value of this protocol in practical application.
Methods:
A total of 645 patients with lung adenocarcinoma from January to December 2008 were selected from the case database of Shanghai Pulmonary Hospital. All patients had complete clinical and follow-up data, and were diagnosed according to the 2015 edition of WHO classification. Among them, 184 cases were AIS/MIA and 461 cases were invasive adenocarcinoma. In accordance with the proposal criteria of the IASLC Pathology Committee Invasion working group, we re-determined the lepidic and invasion pattern mainly according to the definitions of iatrogenic collapse and extensive epithelial proliferation (EEP). The re-diagnosis was mainly based on H&E, and CK7 and elastin staining were added to assist the diagnosis for the cases difficult to identify in H&E. .
Results:
In our case, 4 of the 184 (2.2%) cases originally diagnosed as AIS/MIA were upgraded to invasive adenocarcinoma. All of the 4 cases had a well-defined lepidic like structure, but with luminal epithelial multilayered proliferation(EEP). 32 of the 461 cases (6.9%) originally diagnosed as invasive adenocarcinoma were downgraded to MIA. None of the degraded cases had lymph node metastasis, and the 10-year survival rate was 100%. Interestingly, the four cases with upgraded diagnoses also had good outcomes.
Conclusion:
The understanding of iatrogenic collapse and EEP is helpful to optimize the differentiation of AIS and MIA from invasive adenocarcinoma. The original diagnostic criteria in our hospital tend to be more conservative, and more patients should be diagnosed as MIA under the new criteria are diagnosed as invasive adenocarcinoma, and these patients still have a good prognosis after corrected diagnosis according to the new criteria. The application of the new criteria will allow more patients to benefit from accurate diagnosis.
Professor Xie Huikang’s Comments:
With the increasing use of high-resolution spiral CT, the detection rate of pulmonary nodules is rising year by year, and the number of patients undergoing surgical treatment is also increasing. The pathological diagnosis of these pulmonary nodules will affect patient treatment and prognosis. Currently, there is still significant variation in the diagnostic consistency of early-stage pulmonary adenocarcinoma, lepidic adenocarcinoma, and invasive adenocarcinoma among different pathologists and hospitals, both domestically and internationally. Addressing and reducing this variation to provide patients with accurate diagnoses and treatment is a pressing issue.
The fundamental reason for diagnostic variation lies in the different diagnostic criteria and interpretations of lepidic and invasive patterns among different hospitals. The Invasive Working Group of the IASLC Pathology Committee conducted extensive research over the years and released research results at the end of last year, providing new diagnostic criteria for lepidic and invasive patterns. This new standard primarily emphasizes certain diagnostic concepts, such as iatrogenic alveolar collapse, highlighting that this alveolar collapse is due to external forces and does not represent structural changes caused by true invasion. It also provides specific characteristics for differential diagnosis, such as the concept of extensive epithelial proliferation (EEP). In this concept, some adenocarcinomas can still maintain a lepidic-like morphology, but due to extensive proliferation of their epithelial cells, they are recommended to be categorized as invasive.
This study compared the diagnostic differences between the new diagnostic criteria and the original WHO diagnostic criteria, and evaluated the safety of the new standards in diagnosing in situ and minimally invasive adenocarcinoma, as well as the preliminary exploration of the novel diagnostic concept of extensive epithelial proliferation. Based on the research results, we found that the current new standards have a certain level of safety in diagnosing in situ and minimally invasive adenocarcinoma. Patients reclassified as in situ and minimally invasive adenocarcinoma based on the new criteria did not experience adverse outcomes. Interestingly, the four cases diagnosed with an upgrade due to the presence of EEP also had a good prognosis. This may suggest that further clinical research is needed to validate the standards for extensive epithelial proliferation. Based on our study results, diagnoses made solely according to WHO standards may tend to be conservative, and adopting the new diagnostic criteria will result in more patients being downgraded, leading to better prognostic expectations and reducing unnecessary treatment.
Tongji University, Affiliated Pulmonary Hospital, Associate chief doctor
Member of the Standing Committee of Lung Cancer Professional Committee of Chinese Medical Education Association;
Member of the Respiratory Rehabilitation Professional Committee, Chinese Medical Education Association
Member of Lung Cancer Pathology Group, Special Committee of Tumor Pathology, Chinese Anti-Cancer Association
Member of the Youth Group of the Special Committee of Tumor Pathology, Chinese Anti-Cancer Association
Member of Transplantation Pathology Group, Shanghai Organ Transplantation Society
