**Question:** A 28-year-old woman underwent a fertility-sparing surgery for a 6x6 cm granulosa cell ovarian tumor. Which one of the following will you monitor for detection of recurrence?

A. Serum CA-125 level
B. Pelvic ultrasound
C. Serum beta HCG level
D. Urine beta HCG level

**Correct Answer:**

**Core Concept:**

Granulosa cell tumors are rare, slow-growing neoplasms that originate from the granulosa cells of the ovarian theca layer. They can be hormonally active with production of estrogen, progesterone, or both. For monitoring post-operative surveillance, it is essential to consider the hormone production and the type of surgery performed.

**Why the Correct Answer is Right:**

In this case, the woman underwent a fertility-sparing surgery, which implies that the tumor was removed while preserving the patient's fertility. Hormone production from a granulosa cell tumor can lead to elevated serum levels of beta HCG, estrogen, and progesterone. Among the provided options, measuring serum beta HCG level (Option C) is the most appropriate method for detecting recurrence, as beta HCG is a marker for choriocarcinoma (a subtype of granulosa cell tumor) and is produced by these tumors. Monitoring serum beta HCG levels will help detect any recurrence or residual tumor post-surgery.

**Why Each Wrong Option is Incorrect:**

A. Serum CA-125 level (Option A) is a marker for ovarian cancer but is not specifically sensitive or specific for granulosa cell tumors.

B. Pelvic ultrasound (Option B) is an imaging modality to detect local tumor extension, but does not monitor the hormone production or detect distant recurrence.

D. Urine beta HCG level (Option D) is not commonly used for monitoring post-operative surveillance, as urine beta HCG may be influenced by other factors and has lower sensitivity compared to serum beta HCG.

**Clinical Pearl:**

Monitoring serum beta HCG levels after fertility-sparing surgery for granulosa cell tumors is crucial to detect potential recurrence or residual disease. This is particularly important due to the hormone production aspect of these tumors, and the fact that other markers may not be specific or sensitive enough for this type of tumor.