CA-125 also known as mucin 16 or MUC16 which is a protein in human encoded by the MUC16 gene. MUC16 is a member of the mucin family glycoproteins. CA-125 has found application as a tumor marker or biomarker that may be elevated in the blood of some patients with specific types of cancers, or other conditions that are benign. CA-125 is the most frequently used biomarker for ovarian cancer detection. Around 90% of women with advanced ovarian cancer have elevated levels of CA-125 in their blood serum, making CA-125 a useful tool for detecting ovarian cancer after the onset of symptoms.