Tumor markers are secreted, released, or leaked into the interstitial fluids, and thus into the lymph,
and finally (or directly) into the bloodstream, where they become detectable in serum samples. To be
able to enter the bloodstream directly, larger molecules, often proteins, are cleaved into truncated
forms or fragments, which are sometimes specific to the protease micro-environment of the tumor.
Tumor markers can be associated with patient diagnosis, prognosis, clinical management, and