Abstract
Precision medicine in cancer care is predicated on access to several fundamental pieces of data: (i) a precise tumor diagnosis, (ii) accurate stage classification, and (iii) protein or molecular biomarkers that predict efficacy of targeted therapies. For all patients with cancer, these data points are generated by obtaining a tumor sample and subjecting it to analysis by a pathologist and, when appropriate, a molecular pathologist. While tumor diagnosis and pathologic staging (gross and microscopic examination of the primary tumor and draining lymph nodes) require the infrastructure and expertise of an anatomic pathology program, the advent of "liquid biopsy" has driven a shift in molecular biomarker testing away from local pathology laboratories and into high-throughput, centralized (and often for-profit) laboratories. What does this mean for patient care? How is the role of the pathologist affected? What are the implications for integration of diagnostic information and ultimately for appropriate therapy selection? This article will consider the current testing landscape, address current challenges in the use of liquid biopsy in clinical practice, and consider ways the pathologist should be involved in interpreting liquid biopsy data in the context of the patient's cancer diagnosis and stage.