Sarcoma is a heterogeneous group of cancer of mesenchymal origin, with about 80 % of diagnosed cases being soft tissue sarcoma (STS). The molecular landscape of STSs can range from simple karyotypes to more complex karyotypes such as MDM2 amplification for liposarcoma (LPS), and multiple chromosomal aberrations for undifferentiated pleomorphic sarcoma (UPS). The discovery of circulating cell-free tumor DNA (ctDNA) and in plasma facilitates the use of liquid biopsy as a minimally invasive method to obtain information about the genomic landscape of a tumor. However, ctDNA constitutes only a fraction of the total circulating DNA and high sensitivity methods are required to detect it. Still ctDNA provides a promising new field for diagnosis and prognosis of cancer patients. We used ultra-low pass whole genome sequencing (ULP-WGS) to sequence tumor and plasma for 72 sarcoma patients to detect large DNA copy number aberrations. We also used copy number variation (CNV) droplet digital PCR (ddPCR) to detect increased MDM2 copy number in the plasma of 30 of the LPS patients. Statistical analysis was done to investigate association between detection of ctDNA and clinicopathological parameters.