p16(INK4a) expression analysis as an ancillary tool for cytologic diagnosis of urothelial carcinoma

We immunochemically studied p16(INK4a) expression in 116 urine cytologic samples and compared results with 190 histologic samples. The cytologic samples were classified into 4 groups: 1, mild cellular atypia; 2, moderate cellular atypia; 3, severe cellular atypia; and 4, malignancy. Overexpression of p16(INK4a) was detected in none of 32 cases in group 1, 8 (16%) of 50 cases in group 2, 5 (42%) of 12 cases in group 3, and 11 (50%) of 22 cases in group 4. In addition, by histologic analysis, p16(INK4a) overexpression was not detected in nonneoplastic urothelium, except for a few cases of reactive atypia, but it was detected in about 50% of urothelial carcinomas. In particular, a high incidence (16/20 [80%]) of p16(INK4a) overexpression in high-grade carcinomas was noted in cytologic samples. Immunocytologic analysis of p16(INK4a) expression in cytologic samples is a useful ancillary tool for detection of urothelial carcinoma with infiltrating potential.