Transitional Cell Metaplasia of the Uterine Cervix and Vagina: An Underrecognized Lesion that May Be Confused with High-Grade Dysplasia: A Report of 59 Cases

Sixty-three examples of transitional cell metaplasia of the cervix or vagina from patients 50 to 84 (average 67.6) years of age are described. Fifty-seven of the 59 patients were postmenopausal and two perimenopausal. Only four patients were documented to have received hormonal therapy. The lesion was an incidental microscopic finding in all patients and was found in 29 hysterectomy specimens, 18 endocervical or endometrial curettage specimens, 11 cervical biopsy or cone biopsy specimens, and five vaginal biopsy specimens. The sites involved by transitional cell metaplasia were the exocervix (n = 14), transformation zone (n = 33), vagina (n = 10), or a combination (n = 4). The cervical and vaginal specimens most commonly showed involvement of the surface epithelium by transitional cell metaplasia. Other transitional cell patterns were isolated stromal nests (n = 9) and invagination of surface epithelium into the underlying stroma (n = 2). The typical appearance of transitional cell metaplasia was a hyperplastic epithelium with lack of maturation, consisting of spindled nuclei with tapered ends and frequent longitudinal nuclear grooves. The nuclei were typically oriented vertically in the deeper layers, and horizontally with a streaming pattern superficially. The cells had low nuclear to cytoplasmic ratios, perinuclear halos, and absent to rare mitotic figures. Mild to moderate atypia was seen in only two cases. Many of the cases could have been confused with squamous dysplasia due to the lack of apparent maturation. However, in most cases, attention to cytologic detail disclosed the typical features of transitional cell metaplasia. This process, usually seen in older women, has not been emphasized and can be overdiagnosed as dysplasia, leading to unnecessary treatment.