New Lung Adenocarcinoma Classification in Daily Practice

Abstract

Although histologic criteria remain the foundation of this new classification, it is based on an integrated multidisciplinary platform and defines pathologic entities. One of the novelties is discontinuing the use of the term bronchioloalveolar adenocarcinoma (BAC). New entities are described: "Adenocarcinoma in situ "(AIS) and "Minimally invasive adenocarcinoma (MIA). These modifications of the classification have implications for surgeons with new surgical strategies in the future. For invasive adenocarcinomas, the proposition described here is to present a comprehensive histologic subtyping: individual tumors are then classified according to the predominant pattern and the percentages of the subtypes are also reported. The other part of the work is the establishment of a classification of non-small cell lung carcinomas (NSCLC) for small biopsies and cytology. Subclassification in small biopsies is more problematic. There is however universal agreement that most NSCLC can be classified on H&E stained slides alone without using any immunohistochemical stains and tumors that are readily classifiable on H&E-stained slides should not be stained with immunohistochemical markers because of the obligation for the pathologist to keep tissue for molecular testing. However, some NSCLC are too poorly differentiated to be accurately subclassified by standard H&E criteria. Some markers, especially when used in combination, are indeed useful and accurate in subclassifying poorly differentiated NSCLC. Strategic use of small biopsy and cytology samples is important in order to preserve as much tissues as possible for potential molecular studies. One way to attain this is for each institution to develop a multidisciplinary team that coordinates the optimal approach to obtaining and processing biopsy/cytology specimens to provide expeditious diagnostic and molecular results. In conclusion, the new lung adenocarcinoma classification will not only modify daily practice but will also improve the management of patient.