Subclassifying atypia in urine cytology: what are the helpful features?

The diagnosis "atypical urothelial cells (AUC)" remains an unresolved problem, making many urologists dissatisfied and confused about the management strategy on these cases. To date, a few inspiring attempts were made to subclassify AUC into "atypical urothelial cells of undetermined significance" (AUC-US) and "atypical urothelial cells cannot exclude high grade" (AUC-H). The aim of our study was to investigate the most predictive for high-grade urothelial carcinoma (HGUC) cytomorphologic parameters and whether the proposed classification can be implemented in our institution.

The electronic medical record system was searched for cytology specimens that were diagnosed as AUC from January 1, 2005 to March 1, 2013 and their relative clinical-pathological follow-up. All specimens were reviewed by an experienced cytopathologist by using 20 published "most predictive" for HGUC criteria.

A total of 162 AUC specimens were reclassified into 3 groups: AUC-H (n = 45), AUC-US (n = 51), and "negative for malignancy" (n = 66). The reclassification of AUC-H and "negative for malignancy" had 79% sensitivity, 77% specificity, 60% positive predictive value, and 89% negative predictive value to histologically proven HGUC diagnosis.

Our study demonstrated a good correlation between the presence of "HGUC-predictive" cytologic criteria and the final biopsy-proven HGUC in cytologic cases originally diagnosed as "atypical urothelial cells present." We identified 2 of the most predictive for HGUC on follow-up cytomorphologic parameters such as increased nuclear-cytoplasmic ratio >0.7 and coarse chromatin (16 abnormal cells per slide in average). These parameters, along with positive fluorescent in situ hybridization results can help during cytologic evaluation of urine specimens.