BACKGROUND: Diagnosing patients with severe non-specific symptoms (NSSC) is often challenging. The patients are subjected to extensive testing, and 11 - 35% eventually receive a cancer diagnosis. Liquid biopsies, such as circulating cell-free DNA (cfDNA), pose as a promising non-invasive alternative for cancer detection. Specifically, methylation patterns have shown promising sensitivity and specificity towards cancer as well as tumor origin. This study aims to differentiate between cancer and non-malignant samples by investigating differences in methylation in cfDNA.