A 4-year-old girl is noted to have breast enlargement and vaginal bleeding. On physical examination, she is noted to have a 9-cm pelvic mass. Which of the following is the most likely etiology?

Gynecology and obstetrics are twin subjects that deal with the female reproductive system. While obstetrics deals with pregnancy and its associated procedures and complications, gynaecology involves treating women who are not pregnant. Gynecology comprises of both medicine as well as surgical fields.