Abstract
In the current era of targeted therapy, the diagnosis of non–small-cell lung carcinoma (NSCLC) without further subclassification into adenocarcinoma and squamous cell carcinoma is no longer useful for the optimal management of patients with primary lung carcinoma. Unlike pulmonary squamous cell carcinomas, a significant proportion of pulmonary adenocarcinomas will harbor epidermal growth factor receptor (EGFR) mutation, gene copy number gain, and/or overexpression; these patients are now being treated with EGFR tyrosine kinase inhibitors with improved clinical outcomes. In dealing with lung biopsy samples, pathologists are therefore required to address both of these issues, providing their clinical colleagues with an accurate subclassification of a given tumor sample into adenocarcinoma or squamous cell carcinoma, and to provide a route for EGFR testing on appropriate specimens. In this article, we highlight the heterogeneity of NSCLC with an emphasis on salient cytomorphologic features and ancillary studies used for determining a squamous cell or adenocarcinoma designation. EGFR alterations in primary lung cancer are highlighted, the pros and cons of various testing modalities to document EGFR alterations are discussed, and an algorithm for NSCLC work-up is proposed.
Published Version
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