The significance of smooth muscle bundles in the endocervical submucosa.

In approximately 25% of uterine cervices there are bundles of smooth muscle in the immediate submucosa of the endocervix usually in the region of the transformation zone. They are morphologically and immunohistochemically different from the inherent muscle deeper in the cervix in that they have more cytoplasm, are arranged in bundles not separated by collagen, and do not contain oestrogen or progesterone receptors. They are more commonly found during the reproductive years becoming less common after the menopause, but there is no association with parity, the use of exogenous steroids, uterine fibromyomas or uterine prolapse. At present it can only be concluded that their presence represents a morphological variation.