Circulating tumor cell (CTC) enumeration and characterization have the potential of providing a real-time fluid biopsy which would have widespread implications in the way we currently treat, manage, and even diagnose cancer. Over the past 7 years the Kuhn laboratory has developed an assay to detect CTCs from the blood of cancer patients and has developed new methods and tools to characterize these cells by cytomorphologic and molecular analysis. This laboratory currently has 6 clinical trials ongoing to investigate the incidence and presence of CTCs over time in patients with breast, colorectal, prostate, lung, and pancreatic cancers and how CTC enumeration and characterization correlates with patient response or non-response to treatment. The laboratory is looking for talented graduate students to extend this research to further understand the phenotype and genotype of CTCs in a variety of tumor types as they exist in the blood microenvironment.