**Question:** A 20-year-old female is diagnosed with a granulosa cell tumor of the ovary. Which of the following biomarkers would be useful for the follow-up of the patient?

**Core Concept:** Granulosa cell tumors are rare sex cord-stromal cell tumors of the ovary. These tumors are often hormonally active and can secrete estrogen, progesterone, and/or androgens. Monitoring these hormone levels can help assess tumor activity and response to treatment.

**Why the Correct Answer is Right:** The correct answer, CA-125 (Cancer Antigen 125), is a widely used tumor marker in gynecological malignancies, including ovarian cancer. Elevated serum CA-125 levels are indicative of an increased risk of recurrence or progression of disease in patients with granulosa cell tumors. Monitoring CA-125 levels helps in assessing treatment response and detecting tumor recurrence.

**Why Each Wrong Option is Incorrect:**

A. CA-19-9 (Carbohydrate Antigen 19-9) is a tumor marker used in pancreatic and biliary tract cancers, not ovarian cancer.

B. CA-15-3 (Carbohydrate Antigen 15-3) is a tumor marker for breast cancer, not ovarian cancer.

C. Alpha-fetoprotein (AFP) is a protein produced during pregnancy and elevated levels are associated with liver conditions like hepatocellular carcinoma and yolk sac tumors.

D. CEA (Carcinoembryonic Antigen) is a tumor marker for gastrointestinal and colorectal cancers, not ovarian cancer.

**Clinical Pearl:** Granulosa cell tumors are generally slow-growing and indolent, but monitoring serum CA-125 levels is essential for assessing disease activity and treatment response in these patients. It is crucial to differentiate between increased CA-125 levels due to benign gynecological conditions like endometriosis or pelvic inflammatory disease, which can also raise CA-125 levels.

**Core Concept:** Monitoring of tumor markers (CA-125, CA-19-9, CA-15-3, AFP, and CEA) is essential in the management of ovarian cancer patients to assess tumor burden, response to treatment, and recurrence. Monitoring these markers in granulosa cell tumor patients may provide similar information, but the correct biomarker is CA-125, as it is more specific to ovarian tumors, including granulosa cell tumors.