Cytologic and histologic diagnosis and significance of controversial squamous lesions of the uterine cervix.

The interpretation and precise classification of abnormal squamous cell changes in cervicovaginal smears (Pap tests) and tissue samples are challenging and controversial. The cytologic category atypical squamous cells of undetermined significance and the newly described squamous lesions atypical immature metaplasia, papillary immature metaplasia, and transitional cell metaplasia are representative. Their current status is reviewed, and future directions aimed at resolving some of the controversy and challenge are suggested.