Cancer is the second-leading cause of death in the United States. Metastasis is responsible for 90% of cancer-related death and progresses through multifarious, poorly-understood cascades as they are difficult to observe in vivo. It is widely held that deciphering the metastatic cascade and identifying metastatic precursors will lead to improved patient outcomes. In this work, we isolate and study cancer biomarkers, specifically circulating tumor cells (CTCs) and cancer-cell-derived extracellular shed vesicles (ESVs), implicated in cancer progression and metastasis. First we describe the design, fabrication, and use of a Hele-Shaw microfluidic system to optimize rarecell immunocapture parameters with a focus on informing the design of systems for CTC isolation from patient whole blood. Our study includes the role of antibody selection, density, antigen locations, and multi-modal capture surfaces, as well as shear stress, on rare cell capture. We use LNCaPs, a PSMA-expressing prostate cancer cell line, as a model for CTCs and anti-PSMA antibodies, J591 and J415, to inform chemistry-mediated immobilization. Next, we focus on another cancer-disseminated marker, extracellular shed vesicles. ESVs, including exosomes and cancer-cell-derived microvesicles, are disseminated throughout the body and represent an important conduit of cell communication. Microvesicles have potential as a cancer biomarker as they are believed to transform tumor microenvironments and prime the metastatic niche. Cancercell-derived ESV subpopulations consist of a small-diameter exosome population and a large-diameter, cancer-cell-specific microvesicle population, each formed by unique mechanisms. It is believed that size correlates with biological properties of interest, but isolating these subpopulations, to discern chemical, biological, or physical differences, is challenging. We designed a deterministic lateral displacement microfluidic platform to isolate a pure microvesicle sample from the heterogeneous cancer-cell-derived ESV population. The threshold diameter differentiating the microvesicle population from the exosome population was determined by characterizing the size distributions of ESVs harvested from multiple cancer cell lines of breast, brain, and pancreas origin. Our microvesicle-isolation microfluidic technology facilitates future investigations regarding microvesicles' role in cancer progression by enabling identification of cargo carried by the microvesicle subpopulation.