The new international multidisciplinary histological classification of lung adenocarcinoma and clinical implications for Indian physicians

Abstract

In 2011, a new histologic classification of lung adenocarcinomas (IASLC/ATS/ERS) was proposed based on the recommendations of an international and multidisciplinary panel that included thoracic medical oncologists, pulmonologists, radiologists, molecular biologists, thoracic surgeons and pathologists. This classification proposed a comprehensive histologic subtyping (lepidic, acinar, papillary, micropapillary and solid pattern) and a semi-quantitative assessment of histologic patterns (in 5% increments) in an effort to choose a single, predominant pattern. The prognostic value of this classification has been validated in large, independent cohorts from multiple countries. Patients with adenocarcinomas in situ and minimally invasive adenocarcinomas experienced no recurrence. Patients with micropapillary or solid predominant tumors would be classified as high risk for recurrence or cancer-related death. Patients with acinar and papillary predominant tumors might be classified as an intermediate-risk group, but further investigation is needed for papillary subtype. This classification, coupled with additional prognostic factors (nuclear grade, cribriform pattern, high Ki-67 labeling index, TTF-1 negativity, immune markers and SUVmax on FDG-PET), which we have published on extensively, could further stratify patients into prognostic subgroups that may help with clinical management. This new classification for the most common type of lung cancer is important for oncologists practicing in India, as its implementation would require only hematoxylin and eosin (H&E) histology slides, the most common type of stain used at hospitals. It can be implemented with basic pathologist training and no additional costs. Furthermore, implementation and analyses would identify if this classification is valid for Indian patients or a specific modification is required.