A Nature Communications study mapped circulating tumor DNA (ctDNA) detectability across seven body fluids in metastatic breast cancer, revealing variable sensitivity and representativeness that could reshape sampling strategies for liquid biopsies. Researchers showed that non-blood fluids sometimes capture tumor heterogeneity missed in plasma, informing clinical sampling choices for tumor monitoring and biomarker discovery. Separately, IdentifySensors Biologics validated Check4, an electrochemical graphene-based sensor, for detecting mutant NSCLC genes at sensitivities comparable to FDA-cleared PCR tests and with five-minute readouts. The company demonstrated detection down to 50 copies/mL in model blood samples and plans mass production of cartridges and readers. Together the studies highlight both biological and technological advances that can improve minimal-residual-disease detection and point-of-care oncology diagnostics. Developers should calibrate assay sensitivity to clinical contexts and consider combined platform strategies to capture tumor diversity.