Fibroids are classified based on their location in the uterine wall. Submucous (or submucosal) fibroids occur just under the endometrial lining of the uterine cavity. Intramural fibroids occur in the muscular wall. Subserosal fibroids occur under the outside covering of the uterus. As fibroids enlarge, the distinction between the types becomes blurred.
Pedunculated fibroids (not shown) occur on a stalk, project from the surface of the uterus, and can be confused with ovarian masses. They can project from the inner lining of the uterus and even extend through the cervix.