## **Core Concept**
Malignant ovarian tumors in children are rare, accounting for a small percentage of all ovarian tumors and an even smaller fraction of all childhood malignancies. The majority of ovarian tumors in children are benign, but when malignancy occurs, it often presents with nonspecific symptoms, making early diagnosis challenging.

## **Why the Correct Answer is Right**
Germ cell tumors are the most common type of malignant ovarian tumors in children, and they account for approximately 80-90% of all ovarian malignancies in this age group. The most common types include yolk sac tumors, dysgerminomas, and immature teratomas. These tumors arise from the cells that give rise to the eggs and can produce tumor markers such as alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG), which are useful for diagnosis and monitoring.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it significantly underestimates the percentage of malignancy in ovarian tumors in children.
- **Option B:** This option might seem plausible but still underestimates the high proportion of germ cell malignancies seen in children.
- **Option D:** This option overestimates the percentage of epithelial ovarian tumors, which are more common in adults and rare in children.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that in children, ovarian tumors are more likely to be malignant than in adults, and among these, germ cell tumors are the predominant type. Early diagnosis and staging are critical for management, and tumor markers play a significant role in diagnosis and follow-up.

## **Correct Answer:** C. 80-90%.