Most ovarian tumors in children are benign (noncancerous). The most common cancers that affect the ovaries are of germ cell origin (beginning in cells that give rise to sperm or eggs); these are more common in children than in adults. Common symptoms of ovarian cancer include painful periods and pain in the abdomen. Treatment is stage -related and may include surgery, radiation therapy, and chemotherapy. Sertoli-Leydig cell tumors of the ovary are rare in young girls and may cause development of male sex traits or early signs of puberty. Small cell carcinomas of the ovary are very rare and fast-growing tumors that may cause higher than normal levels of calcium in the blood. Small cell carcinomas may be treated with surgery and chemotherapy, but there are few studies in children.
This answer is based on source information from the National Cancer Institute.