Thin-layer (liquid-based) cytologic findings of papillary squamotransitional cell carcinoma of the cervix. Review of cases over a 4-year period with emphasis on potential diagnostic pitfalls

OBJECTIVE: To describe the thin-layer cytology and diagnostic pitfalls of papillary squamotransitional cell carcinoma of the cervix, with clinical and histologic correlation. STUDY DESIGN: The author reviewed the clinical findings, thin-layer cytology and histologic features of papillary squamotransitional cell carcinoma of the cervix encountered at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during the 4-year period January 1998-March 2002. Strict histologic criteria (basaloid/transitional cell-like cells constituted > 70% of the tumor cell population and papillary/anastomosing, frondlike structures seen in > 70% of tumor tissue in superficial biopsies) were employed in defining this entity. RESULTS: During the study period, 10 biopsy cases of carcinoma of the lower female genital tract (9 in cervix and 1 in vagina) fulfilled the above histologic criteria. Six of them had thin-layer cytology performed The preparations were often of moderate to high cellularity and contained three-dimensional, arborizing, papillary clusters of basal/parabasal cells. Discernible fibrovascular cores were sometimes identified. Occasionally at the papillary surface, the basaloid cells were aligned horizontally. High-power cytology of the tumor cells ranged from bland-looking to high grade squamous intraepithelial lesions (HSILs) and sometimes squamous cell carcinoma. Mitotic figures were commonly identified. Tumor diathesis and dyskeratotic cells were occasional. Koilocytosis was not observed. Subsequent tumor biopsies showed evidence of stromal invasion in 3 cases. CONCLUSION: Papillary squamotransitional cell carcinoma has a distinctive appearance in thin-layer cytologic preparations. The predominance of bland-looking basaloid cells or HSIL cells, together with scantiness of tumor diathesis and carcinoma cells, may lead to underdiagnosis. Recognition of the subtle cytologic features and clinical correlation are essential in arriving at a correct diagnosis.