p16INK4a/Ki‐67 dual labelling as a marker for the presence of high‐grade cancer cells or disease progression in urinary cytopathology

E. Piaton, A. S. Advenier, C. Carré, M. Decaussin‐Petrucci, F. Mege‐Lechevallier and A. Ruffion
p16 ^INK4a /Ki‐67 dual labelling as a marker for the presence of high‐grade cancer cells or disease progression in urinary cytopathology Objective: Overexpression of p16^INK4a independent of the presence of E6–E7 oncoproteins of high‐risk papillomaviruses has been identified in bladder carcinoma in situ lesions with or without concurrent papillary or invasive high‐grade (HG) urothelial carcinoma. As p16^INK4a and Ki‐67 co‐expression clearly indicates deregulation of the cell cycle, the aim of this study was to investigate the frequency of p16^INK4a/Ki‐67 dual labelling in urinary cytology samples. Methods: Immunolabelling was performed in demounted, destained Papanicolaou slides after ThinPrep^® processing. A total of 84 urinary cytology samples (18 negative, 10 low grade, 19 atypical urothelial cells and 37 high grade) were analysed for p16^INK4a/Ki‐67 co‐expression. We assessed underlying urothelial malignancy with cystoscopy, histopathology and follow‐up data in every case. Results: Compared with raw histopathological results, p16 ^INK4a/Ki‐67 dual labelling was observed in 48 out of 55 (87.3%) HG lesions and in 11 out of 29 (37.9%) negative, papillary urothelial neoplasia of low malignant potential or low‐grade carcinomas (P = 0.05). All cases with high‐grade/malignant cytology were dual labelled. Sixteen out of 17 (94.1%) carcinoma in situ cases and eight out of 14 (57.1%) cases with atypical urothelial cells matching with HG lesions were dual labelled. Extended follow‐up allowed three cases of progression to be diagnosed in dual‐labelled cases with negative/low‐grade cytology results after a 9‐ to 11‐months delay. Conclusions: The data show that p16^INK4a/Ki‐67 co‐expression allows most HG cancer cells to be detected initially and in the follow‐up period. Additional studies are needed in order to determine whether dual labelling can be used as a triage tool for atypical urothelial cells in the urine.