Diagnostic Value of Smoothelin and Vimentin in Differentiating Muscularis Propria from Muscularis Mucosa of Bladder Carcinoma

Abstract

Background Determination of the extent of involvement or pathological staging is one of the requirements for adequate evaluation of bladder cancer specimens. Therefore, the differentiation between MP and MM is essential for proper treatment and avoiding over or under staging. Aim The present study aimed at evaluation of diagnostic value of smoothelin and vimentin expression both singly and in combination for differentiation between MM and MP. Methods This study was carried out on 59 cystectomy specimens of primary bladder carcinoma and eleven cystoscopic biopsies for non-neoplastic bladder lesions (cystitis). Results Histologically, MM was identified clearly in 40 cases and MP was identified in all 70 examined cases. The cases were immunostained for smoothelin and vimentin. Intensity of smoothelin expression showed significant difference (P = 0.001) between MM and MP with 97.5% sensitivity and 95% specificity and the percentage of smoothelin expression was significantly higher in MP compared to MM (P = 0.001) with 95.7% sensitivity and 85% specificity (using 65% as cut-off point). Vimentin was negative in MP and showed positive expression in 32 cases (80%) of MM with a statistical significant difference (P = 0.001) providing 80% sensitivity and 100% specificity. Combined moderate to strong smoothelin and negative vimentin offered 100% sensitivity and 100% specificity towards the identification of MP. Conclusions Differentiation of MM from MP can be made based on histopathological criteria, which are unfortunately overlapping in many cases. Moderate to strong smoothelin expression with negative vimentin could be very helpful procedure in difficult and overlapping cases with a high diagnostic validity.