Lung Adenocarcinoma : Histologic Subtypes
Adenocarcinomas of lung show an admixture of many architectural patterns such as acinar, papillary, micropapillary, lepidic, and solid growth patterns (WHO Classification, 2015). The different histologic components are assessed semi-quantitatively in 5% increments in the resected specimen and the tumor is classified based on the predominant component present. Each of the other components are documented in the report due to prognostic implications. The term bronchioloalveolar carcinoma is obsolete and no longer used in the 2015 WHO classification of lung tumors. Histologic subtyping of lung adenocarcinomas is useful when the patient has multiple tumor nodules. It can be used to separate multiple primaries from intrapulmonary metastases. This information can significantly affect staging in patients with multiple lung adenocarcinomas. The image shows invasive adenocarcinoma of lung, lepidic subtype in which the tumor cells spread along the surface of alveolar septa.