CA-125 is a marker antigen for the diagnosis of:
**Core Concept**
CA-125 is a mucin-type glycoprotein that is overexpressed on the surface of ovarian cancer cells, making it a potential tumor marker for the diagnosis and monitoring of ovarian cancer.
**Why the Correct Answer is Right**
CA-125 is produced by the epithelial cells of the ovary, and its levels are often elevated in women with ovarian cancer. The CA-125 antigen is also found in other types of cancers, such as endometrial and breast cancer, but it is most commonly associated with ovarian cancer. Elevated CA-125 levels can be seen in various conditions, including pelvic inflammatory disease, endometriosis, and benign ovarian cysts, but a persistently elevated level in the absence of these conditions may indicate ovarian cancer.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while CA-125 is a tumor marker, it is not specific for any of the listed conditions, and its elevation can be seen in various other conditions.
**Option B:** This option is incorrect because CA-19-9 is a different tumor marker that is associated with pancreatic cancer, not ovarian cancer.
**Option C:** This option is incorrect because while CA-125 can be elevated in endometrial cancer, it is not a specific marker for this condition, and its elevation can be seen in various other conditions.
**Clinical Pearl / High-Yield Fact**
CA-125 levels can fluctuate in women with ovarian cancer, and a single elevated value does not necessarily indicate cancer. A sustained elevation in CA-125 levels over time, particularly in the absence of other explanations, may be a more reliable indicator of ovarian cancer.
**Correct Answer: D. Ovarian cancer**