CA 125 is a blood test used to distinguish whether masses found in the ovaries are benign or malignant (cancerous). However, CA 125 levels can also be elevated in many conditions other than cancer. One such condition is chocolate cysts (endometriomas). Particularly in ruptured chocolate cysts, CA 125 levels can reach very high values and may mimic advanced-stage ovarian cancer due to the cyst contents spreading into the abdominal cavity.