Fibroids originate from the muscle layer of the uterus but they may expand outwards towards the outer layer of the uterus (subserosal) or may largely grow inwards towards the cavity of the uterus (submucosal). Some of these submucosal fibroids may be pedunculated, attached to the muscle layer by a stalk when they are termed fibroid polyps. Very large size fibroids generally involve the whole body of the uterus, distorting the shape of the uterus (intramural).