Immunophenotype of transitional metaplasia of the uterine cervix

Transitional, glandular, and squamous epithelia show distinctive patterns of expression of cytokeratins 13, 17, 18, and 20. Furthermore, some markers, such as cytokeratin (CK) 20 and the asymmetric unit membrane, are related to terminal urothelial differentiation, their expression limited to superficial and occasional intermediate cells. In this study, seven cases fulfilling the morphologic criteria of transitional metaplasia of the uterine cervix were investigated with these markers to determine whether there was evidence of true urothelial-type differentiation in these lesions. Results were consistent and showed clear differences between the squamous, glandular, and metaplastic transitional areas of the cervix. In particular, the expression of CK13, CK17, and CK18 in the metaplastic areas was identical to the pattern observed in normal urothelium. However, full urothelial differentiation was not observed, as CK20 and asymmetric unit membrane were never expressed in the transitional metaplasia. Based on these findings, the term of immature transitional metaplasia would be a more accurate description of this entity.