Fig. 1
From: Liquid biopsy in hepatocellular carcinoma: circulating tumor cells and circulating tumor DNA
CTCs and ctDNA in the peripheral blood. CTCs and ctDNA are the essential elements and are widely believed to be the cornerstones of the liquid biopsy. CTCs are cancer cells that circulate in the bloodstream after being naturally shed from the original or metastatic tumors, they are “seeds” of tumors and can lead to a new fatal metastasis; ctDNA is derived from apoptotic and necrotic tumor cells that release their fragmented DNA into the circulation and contain genetic defects identical to the original tumor cells