Cytological features of transitional cell metaplasia of the lower female genital tract

Abstract

Transitional cell metaplasia (TCM) of the cervix and vaginal vault is rarely reported. We sought to describe the clinical and cytological features and cytological differential diagnosis of TCM. Cervical and vaginal vault smears reported as TCM or smears from patients with histologically confirmed TCM were examined for the following features: cellularity, architecture, background cell population, cell group thickness, cell shape, nuclear features (shape, chromatin, nucleoli, outline), perinuclear haloes, the presence in cell groups of a surface layer of cuboidal cells, and associated pathology. The cases of TCM were compared with smears of conventional atrophy and high grade squamous intraepithelial lesion (HSIL). Six cases (five cervical, one vaginal vault) of TCM were identified from six patients (age range 34-80 years, median 60 years). The smears showed three-dimensional cell groups (2-5 cells in thickness) composed of oval-shaped cells with small amounts of cytoplasm and spindle/oval-shaped nuclei, with the impression of 'streaming' in some groups. The nuclei showed mild membrane irregularities, evenly distributed chromatin, and small nucleoli. Nuclear grooves were identified in at least occasional cells in four cases. A surface layer of cuboidal cells was identified in two cases. The background contained dysplastic squamous cells in three cases. Atrophic changes were present and in one case some cell groups exhibited transition from TCM at one end to more conventional atrophic parabasal cells at the other. Awareness of the cytological features of TCM is critical to avoid a false-positive diagnosis of HSIL, and the consequent ramifications for patients. TCM should always be considered in the differential diagnosis of multilayered cell groups in cervicovaginal smears, particularly in peri- and post-menopausal women and in atrophic conditions.