Lung carcinoma morphology or mutational profile: that is the question

Lung carcinoma represents a heterogenous group of cancers that was for decades simply viewed as small cell carcinoma versus non–small cell lung carcinoma (NSCLC) for diagnostic purposes. This was mainly influenced by the lack of specific therapy for various histologic types and variants of NSCLC. Histologic distinction between adenocarcinoma and other types of NSCLC, particularly squamous cell carcinoma, became important after several milestone reports of epidermal growth factor receptor–tyrosine kinase inhibitor (EGFRTKI) efficacy in lung adenocarcinomas were published. 1–3 Since these initial reports about clinicopathologic characteristics of responders to EGFR-TKIs, several studies have attempted to better define the morphology of adenocarcinomas occurring in patients with EGFR and KRAS mutations. Initial reports indicated that EGFR mutations were most frequently observed in bronchioloalveolar carcinomas. 4–6 However, studies that applied the strict