Submucosal fibroids are the least common type of uterine fibroids, intramural and subserosal types being the other. It accounts for just 5% of all fibroids and are always symptomatic. Submucosal fibroids can occasionally become pedunculated and prolapse into the cervical canal or vagina.
On ultrasound submucosal fibroids are seen as hypo-echoic solid masses with shadowing located at the myometrial endometrial juncture. Submucosal fibroids typically have an overlying layer of echogenic endometrium, which helps confirm their subendometrial location and helps distinguish them from endometrial polyps. In addition, as opposed to polyps, submucosal fibroids often distort the interface between the endometrium and myometrium and show acoustic attenuation.
Because of its subendometrial location, hysteroscopic myomectomy is a preferred and more successful procedure in cases of submucosal fibroids.
For a complete discussion on submucosal fibroids please see: sub-mucosal leiomyoma of the uterus.