General Medical Information

Ovarian Morphology

Andrew S. Cook

Follicular growth in infancy and childhood has been documented by both morphologic and sonographic studies. An interesting study by Peters histologically evaluated 52 ovaries at autopsy of children who died in an accident or after an acute illness. The children ranged in ages from 2 months to 11 years. Ovarian growth was classified as (a) quiescent—small, resting follicles, with no growth; (b) early growth—preantral follicles present but not larger than 0.5 mm in diameter; and (c) actively growing—with antral follicles larger than 0.5 mm and evidence of degeneration and “scars.” None of the ovaries were quiescent; three were in early growth and 49 of 52 were actively growing. Antral follicles measuring 3, 4, and 5 mm were commonly seen at all ages. The authors subjectively believed that both the number and size of antral follicles increased after the age of 6 years.

The ovarian architecture of infants and premenarcheal children has been evaluated sonographically. Ovaries can be classified as follows: the homogeneous ovary is void of cystic structures; the microcystic ovary has cysts smaller than 9 mm; and the macrocystic ovary has at least one cyst larger than 9 mm. Follicular activity is noted from early childhood, with an increasing percentage of children demonstrating microcystic ovaries with increasing age. Macrocystic ovaries were not observed before 12 years of age. Stanhope defined a megalocystic ovary as containing more than six follicles larger than 4 mm. They noted a progressive increase in the proportion of megalocystic ovaries in normal premenarcheal girls over the age of 8.5 years. This study considered as abnormal ovarian cysts larger than 9 mm in diameter in girls less than 12 years of age. Ovarian cysts larger than 9 mm are seen in 12- and 13-year-old girls, even if they are premenarcheal. In a more recent study, 155 ovaries in 101 children ages 2 to 12 years of age were evaluated sonographically. On average, 68% of ovaries were cystic, with no age group having less than 53% prevalence of cystic ovaries. Macrocystic ovaries were noted approximately 10% of the time. The highest incidence of macrocystic ovaries was observed in girls 3 and 8 years old. The author of this study believed that the discrepancy in the incidence of macrocystic ovaries might be a result of improved sonographic technologies and resolution.

Most large ovarian cysts up to the age of 2 years are functional cysts. Between the ages of 5 and 15 years, most complex ovarian masses are teratomas, 30% of which are malignant.

Computed tomographic (CT) evaluation of 125 normal girls revealed microcystic ovaries (cysts smaller than 9 mm) in 71% of ovaries visualized in girls under 8 years of age and 84% of ovaries in girls 8 years of age or older. Macrocystic ovaries (cyst larger than 9 mm) were seen in 12.5% of ovaries in girls 8 years of age or older.