What is being measured
Tumours can release fragments of DNA into the bloodstream. Liquid biopsy detects and analyses this circulating tumour DNA, along with other blood-based markers.
It is minimally invasive and can be repeated over time, which makes it attractive when tissue is difficult to obtain or when change needs to be followed.
Why tissue still matters
A negative blood result does not exclude an alteration; the amount of tumour DNA in circulation varies. Tissue biopsy remains necessary in many situations, particularly for diagnosis and pathology.
Liquid biopsy is best understood as complementary, not as a replacement.