Most common ovarian tumor -

Serous tumors are the most common of the ovarian epithelial tumors. About 60% are benign, 15% are of low malignant potential, and 25% are malignant. Benign lesions are usually encountered in patients between 30 and 40 years of age, and malignant serous tumors are more commonly seen between 45 and 65 years of age. Taken together, borderline and malignant serous tumors are the most common ovarian malignancies, accounting for about 60% of all ovarian cancers. ref : Robbins Basic Pathology, 9E,page-697