CA 125 and CA 15-3 are both tumor markers used in cancer diagnosis and monitoring. CA 125 specifically refers to cancer antigen 125, which is primarily associated with ovarian cancer. Elevated CA 125 levels may also be found in other conditions, such as endometriosis or pelvic inflammatory disease. On the other hand, CA 15-3, or cancer antigen 15-3, is primarily associated with breast cancer. Similar to CA 125, CA 15-3 levels can also be elevated in non-cancerous conditions, making it important to consider other diagnostic tests and imaging studies for accurate assessment.