The tumour markers currently in clinical use, such as α-fetoprotein (AFP) in HCC and prostate-specific antigen (PSA) in prostate cancer, show insufficient sensitivity and specificity to be effective in early diagnosis of the cancer.4, 5, 6, 7, 8 Emerging tumour markers such as circulating tumour DNA (ctDNA) or cell-free RNA, hold promise to enable more accurate early tumour diagnosis in the future.7, 8, 9, 10 Major limitations of the early detection of tumours by tumour-released markers are elevated blood levels from non-malignant conditions (e. Here, KLK3 is linked to hepatocellular carcinoma.