PIK3CA Mutational Analysis in Formalin-Fixed, Paraffin-Embedded Archival Tissues of Urothelial Carcinoma of Urinary Bladder

Objective: Urothelial carcinoma of the urinary bladder is the fourth most common cancer in males inthe United States. In addition to mutations in FGFR3, TP53, AKT1, TSC1, and PTEN genes, mutationsin PIK3CA have been also described in urothelial carcinomas, preferentially in low-grade tumors. Herein,we evaluated the presence of PIK3CA mutations in exons 1, 9, and 20 in 21 urothelial carcinomas of theurinary bladder. Methods: Patients were treated by radical cystectomy without neoadjuvant chemotherapy.Representative tissue blocks (1 for each case) were selected. We used a pinpoint DNA extraction techniquefrom formalin-fixed, paraffin-embedded and mutational analysis using the polymerase chain reaction (PCR)assay coupled with sequencing of targeted exons. Patients included 15 men and 6 women, with a median ageof 68 years (range, 42 to 76 years), with 3 noninvasive and 18 invasive urothelial carcinomas. Noninvasivecarcinomas included 1 case each of low-grade papillary urothelial carcinoma, high-grade papillary urothelialcarcinoma, and urothelial carcinoma in situ (CIS). Invasive tumors included 3 pT1, 5 pT2, 6 pT3, and 4 pT4urothelial carcinomas. Results: We did not find mutations in the analyzed exons of the PIK3CA gene, inany of the 21 urothelial carcinomas. The preponderance of invasive high-grade and high-stage tumors couldexplain the absence of identifiable mutations in our cohort. Conclusions: PIK3CA mutations as prognosti-cators of outcome or predictors of therapeutic response await further evaluation.