The overwhelming majority of ovarian masses are benign and the lifetime risk of developing ovarian cancer is about 2%. Age is the most important factor in determining risk of malignancy. Adnexal masses are common during the reproductive years. During this stage of life, such masses are usually caused by functional ovarian cysts, benign neoplasms of the ovary or by postinfectious changes in the fallopian tubes. In girls under 20 and in women over 50, about 10% of all palpable ovarian masses are malignant. Between 85 and 90% of ovarian cancer occurs in postmenopausal women.

Benign neoplasms of the ovary

Benign and malignant neoplasms can develop from any cell type found in the ovary. Simple cysts can be functional and form at the site of ovulation or during the development of the corpus luteum. These are very common and distinguishable from true neoplasms by their transitory nature. They typically disappear within 6 weeks of discovery. Complex or solid masses and those that are persistent are more likely to be truly neoplastic and require histologic diagnosis.

Dermoids are a unique type of benign ovarian tumor that arises from more mature germ cells than the other germ-cell tumors (GCTs) found in women (Table 42.1). On gross examination, dermoids may contain hair, bone, cartilage and large amounts of greasy fluid that rapidly becomes sebaceous at room temperature. On histologic examination, the tumors contain disarrayed clusters of many of the cell types normally seen in fetuses. Like other GCTs, the molecular event(s) that lead to activation of the germ cells in dermoids can occur in utero and benign ovarian teratomas have been detected in the fetus and newborn infant. Ovarian dermoid tumors display abnormalities in imprinting and are discussed in more detail in Chapter 45.

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