Types of Fibroids
Fibroids are commonly classified based on their size and location relative to the uterus.¹⁻² There are four types of fibroids: intramural, subserosal, submucosal, and pedunculated. Each are explained below so you can understand the difference between the main types of fibroids. Most women with uterine fibroids have more than one type of fibroid.¹
Intramural fibroids, the most common type of fibroid, grow in the wall of the uterus. They may eventually enlarge to distort the uterine cavity or serosal surface. Some fibroids may be transmural, meaning that they extend from the serosal to the mucosal surface.
Subserosal fibroids grow on the outside of the uterus. As they grow larger, they can cause pain due to their size and the pressure that they put on nearby organs.
Submucosal fibroids grow just underneath the uterine lining and can crowd into the uterine cavity, leading to heavy bleeding and other more serious complications.
 Munro, M. G., Critchley, H. O. D., & Fraser, I. S. (2011). The FIGO classification of causes of abnormal uterine bleeding in the reproductive years. Fertility and Sterility, 95(7), 2204–2208.e3.