Evolving molecular techniques used in the clinical laboratory are becoming increasingly important across nearly all fields of medicine. An increased understanding of carcinogenesis and the use of targeted cancer therapies has resulted in a demand for new types of molecular oncology test to help in cancer diagnosis and as tools to predict response to targeted therapeutics for cancer patients. Understanding the need for and the function of these emerging molecular oncology tests by both clinicians and laboratorians is often problematic. Although many of these molecular testing techniques and strategies are relatively new to oncology, similar testing has been performed in the field of infectious diseases for many years and is now widely accepted and understood. Recognizing the parallels between the molecular testing that is now standard for infectious diseases and testing being introduced to aid in the care of cancer patients will accelerate the acceptance, implementation and correct utilization of molecular assays for oncology.