BACKGROUND. Transitional cell metaplasia of the uterine cervix is an under-recognized entity in cervical pathology. The underlying etiology and biologic significance remains uncertain. The thin-layer cytology findings and association with human papillomavirus (HPV) have not been studied thoroughly. METHODS. The authors retrospectively reviewed the clinical findings, thin-layer cytology and histologic features of pure transitional cell metaplasia of the uterine cervix occurring in seven perimenopausal or postmenopausal Chinese women at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during the period from January, 1998 to April, 2001. Molecular techniques for HPV screening and genotyping using polymerase chain reaction and restriction fragment length polymorphism analysis were employed in the thin-layer cytology specimens and paraffin block material. RESULTS. In all seven patients, transitional cell metaplasia represented an incidental histologic finding. It occurred in the ectocervix, transformation zone, endocervix, or vagina. Histologically, it resembled urothelium of the urinary bladder and was comprised of multilayers of mitotically inactive, immature epithelial cells with vertically aligned oval nuclei, fine chromatin, indistinct nucleoli, and conspicuous longitudinal nuclear grooves. The superficial cells were oriented more horizontally and contained pale-staining cytoplasm similar to umbrella cells. Features consistent with transitional cell metaplasia were identified in two of seven preoperative thin-layer preparations. Cytologically, the affected parabasal cells recapitulated the features that were seen in histologic sections. In addition to the bland nuclear morphology and longitudinal nuclear grooves, the cell borders appeared distinct, and the appearance of a perinuclear cytoplasmic halo was common. Sometimes, the metaplastic cells assumed a spindle shape and appeared as cohesive, streaming cell clusters. Molecular study successfully demonstrated the presence of HPV in all seven patients, mostly in the liquid-based cytology samples. In general, the viral DNA load was relatively low; and, for samples in which HPV genotyping was feasible, HPV type 58 was the prevalent genotype. CONCLUSIONS. The current study demonstrates that transitional cell metaplasia of the uterine cervix is related to HPV. It also carries a distinctive cytologic appearance in thin-layer preparations. Based on the limited follow-up data from a small number of reported patients, transitional cell metaplasia seems to run an indolent clinical course. However, its peculiar association with HPV and its possible correlation, both morphologic and histogenetic, with cervical intraepithelial neoplasia need further investigation. Cancer (Cancer Cytopathol) 2002;96:250-8.
