Impact of density of schistosomal antigen expression in urinary bladder tissue on the stratification, cell type, and staging, and prognosis of carcinoma of the bladder in Egyptian patients.

Background: Infection with urinary schistosomiasis and its severity are oncogenic factors for developing carcinoma of the bladder, whether it is urothelial carcinoma (UC) of a transitional cell type (TCC) or non-urothelial of squamous cell carcinoma (SCC). In UC it is not defined whether it is schistosomal or not. This led to controversial results in expression of tumour markers, tumour prognosis, and response to therapy.

Objectives: We assessed the application by immunohistochemistry method (IHC) for detection of schistosomal antigen in bladder cancer tissue samples to differentiate UC associated with or without schistosomiasis. Urothelial carcinoma stage, grade, and progression were correlated with the density, intensity, and index of schistosomal antigen expression. Follow up was done for 2-5 years.

Design And Participants: Archival tissue samples of 575 patients were studied: 515 urothelial carcinoma, 30 patients with SCC associated with schistosomiasis, and a control group of 30 patients without schistosomiasis.

Measurements: Expression of schistosomal antigen in tissue was done by IHC using monoclonal antibodies (MAbs) against schistosomal antigens (SA). Correlation of intensity of antigen expression to clinical and pathological data was analysed.

Results And Limitations: We identified 3 parameters of antigen expression: density, intensity and index with 4 grades for each. SCC-group was 100% positive. UC was positive in 61.4% distributed as follows: Ta: 37.5%, T1: 62%, and muscle invasive T2-4 were 64%. Upstaging, metastases and recurrence were correlated with high index in T1 and T2-4 tumours.

Conclusion: Urothelial carcinoma associated with schistosomiasis was defined by the positive expression of schistosomal antigens in tissues detected by lHC using MAbs against schistosomal haematobium. Upstaging and progression of T1 and T2-4 were correlated with high density, intensity, and index of antigen expression. Non-schistosomal UC had negative expression for schistosomal antigen, which was detected in 36.5% of cases. These results would be of significance in differentiating schistosomal from non-schistosomal bladder cancer of UC and would predict the prognosis in T1, T2-3 tumours. Implementation of IHC using MAbs against SA in UC would help in planning the proper therapy. Schistosomiasis should be considered as an oncogene for UC in endemic areas.