Fibroids are benign tumours that grow in the muscle wall of the uterus. They are called leiomyoma or myomas. They are very common, and are detectable in about 30% of woman over the age of 30. Fibroids range in size from tiny to large, and are often in multiples. Fibroids do not always cause a problem and do not always need to be removed. They usually decrease in size after menopause, as they are oestrogen dependent. Fibroid Patient Information.