While histopathology has traditionally been the cornerstone of treatment decisions in the management of lung cancer patients, the complexity and heterogeneity of histological classification has had a limited impact in the routine practice of oncology. This has changed dramatically in the last few years, owing to discoveries of genomic aberrations and results of clinical trials of novel and targeted therapies. These discoveries have resulted in a new way of classifying non-small cell lung cancer (NSCLC), based on the occurrence of putative or proven driver and targetable genomic changes. The rapidity by which the landscape of mutation and genomic changes is being identified also has led to a new paradigm and approaches to pathological diagnosis of NSCLC. In this context, international consortia have proposed new classifications of lung adenocarcinoma and guidelines for molecular testing in lung cancer and have provided concrete recommendations on new ways to practice lung cancer pathology.