ANIMAL MODEL Adenosis and Clear-Cell Carcinomas OF of Vagina and Cervix HUMAN DISEASE Animal Model: Estrogen-Induced Adenosis of Vagina and Cervix in Nlice Contributed by. John-Gunnar Forsberg, MD, Institute of Anatomy, Arstadvollen, Bergen, Norway. Biogic Features Beginning in the late 1940s, nonsteroidal estrogens (diethlstilbestrol, hexestrol, dienestrol) were commonly used in the United States for the treatment of high-risk pregnancies. In the period 1965-1970, an increase w-as noted in the incidence of clear-cell adenocarcinomas (CCA) of the uterine cervix and vagina in young female offspring. In 1971, a close association was demonstrated between ingestion of diethvlstilbestrol (DES) by the pregnant mother and development of CCA in the offspring.' The risk of developing CCA seems to be low in the exposed population and is estimated to be less than 4 in 1000.2 Both the incidence of CCA and type of tumor mav change when the population grows older.3'4 About tw%o-thirds of the CCAs have arisen in the vagina, especially in its upper and middle thirds, and one-third in the cervix.2'5 The histologic picture is dominated by solid, cystic, and tubular patterns; the dominating cell type is a clear, hobnail-shaped cell.' Nonneoplastic changes associated with CCA are, e.g., cervical erosion and vaginal adenosis (97% for vaginal and 52% for cervical CCA2). In the whole population exposed to DES, the incidence of adenosis is about 30% or even much higher.5'6 This condition is uncommon in unexposed women.7 Animal Model Changes similar to those described in w-omen can be induced in mice by neonatal estrogen treatment. Female mice belonging to a closed colony of Publication sponsored b- the Registn- of Comparative Pathology of the Armed Forces Institute of Pathology and supported by Public Health Service Grant RR 00301 from the Division of Research Resources. US Department of Health. Education and 's-elfare. under the auspices of U niversities Associated for Research and Education in Pathology. Inc 669 670 FORSBERG American Journal of Pathology Figure 1-Section through the uterine cervix of a 1-month-old mouse injected wfth estradiol neonatally. Note the regions with columnar epithelium. (x 70) Figure 2-Uterine cervix from a 2-month-old mouse injected with estradiol neonatally. The ectopic columnar epithelium in the cervix has a wavy appearance, indicating the tendency to form downgrowths. A small glandular downgrowth can be seen. (x 70) Figs 3 and 4-Adenosis regions with different appearances as seen in 6-month-old animals injected with estradiol neonatally. (3, x 60; 4, x 25) Figure 5-Ectopic cervical epithelium with wavy appearance in a 2-month-old mouse injected with DES neonatally. (x 70) Fgure 6-Thirteen-month-old mouse injected with DES neonatally. The whole cervical wall is penetrated by grandular ducts and cysts. An epidermization has occurred in parts of the cystic wall and in the glandular ducts. (x 70) Vol. 84, No. 3 CLEAR-CELL CARCINOMA 671 Septembe 1976 the NMRI strain (no systematic sister-brother mating) are used. Begin- ning within 24 hours after birth, and later with a 24-hour interval for the first 5 days after birth, neonatal females are injected subcutaneously with 5 gg estradiol-17, or 5 Mg DES in olive oil. Controls are given olive oil only. The hormonal treatment results in central and peripheral effects.8" The former are evident as an ovary-dependent persistent vaginal cornification because of effects on hypothalamic differentiation. The peripheral effects occur in the genital epithelia. At puberty, the squamous epithelium in the uppermost part of the vagina, in the vaginal fornices, and in the uterine cervix, is replaced in more or less extensive regions, by columnar epithe- lium. Later, this epithelium forms glandular downgrowths into the stroma resulting in adenosis: tubular, often whorled, and densely packed struc- tures with a tendency to cyst formation.' The adenosis may penetrate deeply into the stroma, in extreme cases reaching the mesothelial surface. Castration at puberty prevents development of adenosis, but the colum- nar, ectopic surface epithelium remains. Treatment with DES results in the same type of changes as from estradiol but more extensive.10 There is suggestive evidence for stromal invasion from adenosis, espe- cially impressive in 13-month-old animals which were treated with DES when newbom. In the latter animals the picture is consistent with malig- nant development in both the glandular epithelium and in seemingly epidermized regions in the adenosis, resulting in squamous carcinoma.1" Compison Wih Hunan Disea The vaginal epithelial development in man and mouse have common traits.8'14 An estrogen-induced inhibition of proliferative activity in the human columnar vaginal epithelium (at the Millerian stage) could be expected to result in adenosis. In both man and mouse, the differentiation process proceeds upwards in the anlage. This means that the sensitive period is of longest duration in the upper vagina and exocervix in man and in the cervix of mice; estrogen-induced changes should be expected to occur with the greatest frequency in the same regions. In practice, this is true. 2,5,9 The average age of patients presenting symptoms of CCA is about 17 vears. This may indicate that hormonal factors play a role for devel- opment of CCA. In mice, adenosis is influenced by ovariectomy, and hormones have also been included in discussions on human adenosis.7 HoweVer, the relation between CCA and adenosis is far from clear; in the model, a malignant transformation within adenosis is suspected."1 The cytology of adenosis in mouse and man shown similarities; in both 672 FORSBERG American Journal of Patlology species the glandular structures contain cells similar to those in the endometrial epithelium, and in both species adenosis is accompanied by an inflammatory reaction.' The hobnail cells, typical of CCA and resem- bling Arias-Stella cells of pregnancy, have not been observed in the mouse. euhss Of th mod The animal model allows experimental analysis of different important factors: the cell differentiation process in the cervicovaginal epithelium, factors responsible for the difference in response to estrogen between the Mulllerian cervicovaginal epithelium and the uterine epithelium, and factors influencing the fate of adenosis. Refernes 1. Herbst AL, Ulfelder H, Poskanzer DC: Adenocarcinoma of the vagina: Association of maternal stilbestrol therapy with tumor appearance in young women. N Engl J Med 184:8784-81 1971 2. Herbst AL, Robboy SJ, Scully RE, Poskanzer DC: Clear-cell adenocarcinoma of the vagina and cervix in girls: Analysis of 170 Registry cases. Am J Obstet Gynecol 119:713-724, 1974 3. Stafl A, Mattingly RF: Vaginal adenosis: A precancerous lesion? Am J Obstet Gynecol 120:666-673, 1974 4. Fetherston WC: Squamous neoplasia of vagina related to DES svndrome. Am J Obstet Gynecol 122:176-180, 1975 5. Scully RE, Robboy SJ, Herbst AL: Vaginal and cervical abnormalities, including clear-cell adenocarcinoma, related to prenatal exposure to stilbestrol. Ann Clin Lab Sci 4:222-233, 1974 6. Sherman Al, Goldrath M, Berlin A, Vakhariya V, Banooni F, Michaels W, Goodman P, Brown S: Cervical-vaginal adenosis after in utero exposure to synthetic estro- gens. Obstet Gynecol 44531-545, 1974 7. Kurman RJ, Scully RE: The incidence and histogenesis of vaginal adenosis: An autopsy study. Hum Pathol 5:265-276, 1974 8. Forsberg J-G: Induction of conditions leading to cancer in the genital tract by estrogen during the differentiation phase of the genital epithelium. Adv Biosci 13:139-151, 1974 9. Forsberg J-G: The development of atypical epithelium in the mouse uterine cervix and vaginal fornix after neonatal oestradiol treatment. Br J Exp Pathol 50:187-195, 1969 10. Forsberg J-G: Estrogen, vaginal cancer, and vaginal development. Am J Obstet Gynecol 113:83-87, 1972 11. Forsberg J-G: Late effects in the vaginal and cervical epithelia after injections of diethylstilbestrol into neonatal mice. Am J Obstet Gynecol 121:101-104, 1975 12. Forsberg J-G: Cervicovaginal epithelium: Its origin and development. Am J Obstet Gynecol 115:1025-1043, 1973.