Comparative studies of squamous metaplasia of the cervix uteri and endometrium

Abstract

The experimental induction of so-called squamous metaplasia in the rat uterus suggests the existence of two distinct processes which bring about this transformation, and they may be used as prototypes for the study of this change in other organs and species.{ce:italic}Indirect regenerative squamous metaplasia{/ce:italic} is a reparative process resulting as the final phase of a destructive lesion. In its early stage it appears as multiple small islands of squamous cells in areas of degenerating or necrotizing epithelium. The causes are numerous and are nonspecific. It occurs following chronic inflammation, atrophy, trauma, excessive and prolonged hormonal stimulation, and vitamin A deficiency. It is found in the mucosa of many organs, and notably in the endometrium where multiple foci of squamous epithelium have been observed accompanying hyperplasia endometrii, adenomatous carcinoma of the fundus, endometrial polyps, chronic endometritis, and tuberculous endometritis. It has been induced experimentally by several procedures in various laboratory animals.{ce:italic}Prosoplasia{/ce:italic} is a name given in this study to an orderly progressive development in the course of which the original mucosa of an organ becomes stratified in a characteristic manner and eventually differentiates into mature squamous epithelium. The process is a specific direct result of estrogenic hormone stimulation and is found both in the human and in experimental animals. It has been observed in the urethra, paraurethral glands, Bartholin's glands, vagina, and cervix uteri of the female of many species. In the male it has been found, and induced experimentally with estrogens, in the urethra, prostate, Cowper's glands, and seminal vesicles of men and many animals. There is evidence that in both sexes this distribution is limited to organs and tissues which are derived from the embryonic urogenital sinus.