Transitional (urothelial) cell metaplasia of the uterine cervix: morphological assessment of 31 cases.

Thirty-one cases of transitional cell metaplasia (TCM) of the uterine cervix were studied. The mean age of patients was 62 years (range 30-87); 25 (81%) were postmenopausal and six premenopausal. In 24 of 25 postmenopausal patients, TCM was an incidental finding at operation for a variety of gynecological lesions, and in such patients the distribution of TCM included the endocervical canal, transformation zone, native ectocervix and vagina. In five of six premenopausal patients, TCM was identified in the cervices of women investigated for abnormal Papanicolaou smears. In all six premenopausal patients, as well as in the remaining postmenopausal patient who also presented with an abnormal Papanicolaou smear, TCM was confined to the endocervical canal and transformation zone. TCM was typified by a multilayer epithelium, clearly distinguishable from the atrophic ectocervical epithelium of most postmenopausal patients by its thickness (averaging 12 cells thick). TCM was identified on the surface epithelium or in sequestered endocervical glands resembling Walthard cell nests of the fallopian tube serosa. There was loss of the usual basal "picket fence" layer seen in cervical squamous epithelia; the cells had crowded nuclei oriented vertically and swirling to give a superficial appearance of disorder. Although lack of "differentiation" from the basal to superficial layers was characteristic, in many examples there was an obvious surface umbrella layer. Intraepithelial glandular differentiation and lesions resembling cystitis glandularis of the urinary bladder were occasionally noted on the ectocervix and vagina. Cellular detail included large pale oval nuclei, oriented vertically, with finely stippled chromatin, small inconspicuous nucleoli, and frequently a deep longitudinal groove. Although the nuclear/cytoplasmic ratio was high, cell-to-cell variation was negligible, and mitoses were rare and never atypical, which, with the nuclear details, distinguished TCM from high-grade squamous dysplasias. The nature of the metaplasia and its biological function are unclear. In postmenopausal patients, it presumably arises occasionally as a consequence of the altered hormonal environment of the cervix and vagina and is of interest only for the possibility of misinterpreting it as a high-grade squamous intraepithelial lesion. In premenopausal patients, it may represent a cellular variation of either physiologic or atypical metaplastic squamous epithelium of the cervical transformation zone.