Hyperchromatic crowded groups in cervical cytology--differing appearances and interpretations in conventional and ThinPrep preparations: a study from the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology.

Abstract

CONTEXT: The practice of gynecologic cytology requires that high-grade squamous intraepithelial lesion (HSIL) be precisely recognized. In this regard, hyperchromatic crowded groups are known to be difficult to classify in conventional gynecologic cytology, but whether this is true in ThinPrep specimens is uncertain. OBJECTIVE: To assess whether hyperchromatic crowded groups of cells in challenging HSIL cases are a problem in ThinPrep preparations, and whether these groups differ in appearance from those of conventional smears. DESIGN: Sixteen images were taken from both conventional smears and ThinPrep slides that had a reference diagnosis of HSIL in the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology, but had performed poorly on subsequent participants' reviews. These 32 representative images were of hyperchromatic crowded groups and were classified by 20 Cytopathology Resource Committee members (17 pathologists and 3 cytotechnologists), who were masked to the reference diagnosis. A consensus classification was derived using the majority opinion of the individual reviewers. Finally, 5 cytologic features were assessed for those images that were interpreted as abnormal by the consensus classification. RESULTS: None of the 32 images was uniformly interpreted as either benign, squamous lesion, or glandular lesion on individual review. Only 27% of individual interpretations of conventional smear images and 15% of ThinPrep images were interpreted as HSIL/squamous cell carcinoma (P < .001). Individual interpretations of ThinPrep images as glandular lesions (60%) were more often made than those of conventional smears (44%, P < .001). The consensus interpretation of ThinPrep images was glandular lesion in 75% of cases, whereas fewer than 50% of the consensus interpretations of conventional smear images were in this category. Conventional smear images were characterized by elongate nuclei (43%) and large nuclei (71%), whereas ThinPrep images more often showed rounded smooth edges (53%) and small nuclei (80%), and were recognized as a glandular lesion. CONCLUSIONS: Hyperchromatic crowded groups of cells are a source of difficulty in challenging HSIL cases for both conventional smears and ThinPrep specimens. In conventional smears, these groups are more likely to be labeled as a squamous lesion, owing to their elongate and large nuclei. In ThinPrep specimens, however, these groups are more likely to be labeled as glandular lesions, owing to their smooth contoured borders and small nuclei.