Evaluation of pelvic washing specimens in patients with endometrial cancer: Cytomorphological features, diagnostic agreement, and pathologist experience

Background Pelvic washings for patients with endometrial cancer is recommended but not used for staging. The International System for Reporting Serous Fluid Cytology (TIS) has standardized diagnostic categories, but the criteria remain incomplete. The 3 primary goals of this study were to 1) investigate features that distinguish atypical/indeterminate from malignant specimens, 2) measure the level of agreement between chart and reviewer diagnoses, and 3) determine whether the number of years in practice had an effect on the diagnoses rendered. Methods Pelvic washings and surgical pathology specimens for 52 patients with a chart diagnosis of atypical/indeterminate, suspicious, or malignant cytology and 52 age‐matched controls with a negative chart diagnosis were included, reviewed blindly by 2 cytopathologists, and assigned a study diagnosis. Morphologic features were assessed. Agreement between original chart diagnoses and reviewer diagnoses were assessed as well as effect of years in practice. Results The overall cellularity in cell block (CB) slides for the malignant category was significantly increased compared with the atypical/indeterminate category (P < .0001). In addition, the number of atypical groups in ThinPrep for malignant washings was significantly increased compared with the atypical category (P < .001) and the negative and suspicious categories (P < .0001) in the CB. Overall agreement between the original and adjudicated diagnoses was high (γ = 0.983). There was no significant difference between diagnoses rendered and years in practice. Conclusion The overall cellularity and number of atypical cells can be used to distinguish between malignant and atypical pelvic washing specimens. There is high reproducibility in the diagnostic categories and high agreement among pathologists, regardless of practice experience. These findings can help refine the criteria for TIS. There are cytologic features, such as total cellularity and the number of atypical groups, that differ between atypical/indeterminate and malignant pelvic washing specimens in patients with endometrial cancer. There is high diagnostic precision among pathologists in diagnosing these pelvic washing specimens. These findings may aid in determining criteria for the newly reported TIS system.