Although the differentiation between high-grade urothelial carcinoma (UC) and high-grade prostatic carcinoma (PC), especially in small biopsies, is challenging, a definite diagnosis is mandatory as the distinction between both entities has significant impact on the patient management.Aim
The aim of the present study was to identify the best immunohistochemical marker(s) that can differentiate between these two entities.Materials and methods
We applied an immunohistochemical panel using the newly described marker GATA3 (GATA binding protein 3), as well as p63, CK7, and CK20 as UC markers and the newly discovered marker AMACR (α-methylacyl-CoA-racemase) with prostate-specific antigen (PSA) as a PC marker. This study was conducted on 38 high-grade UC cases and 34 high-grade PC cases.Results
GATA3 was a highly specific UC marker with diffuse staining pattern, specificity of 100% and diagnostic accuracy of 91.6%. It was followed by p63, which showed patchy staining, specificity of 100% and diagnostic accuracy of 83.7%. CK7 showed either diffuse or patchy staining with specificity of 91.2% and diagnostic accuracy of 80.6%. CK20 showed mostly patchy staining, with a much less diagnostic accuracy of 68% than those of all other UC markers that were used. Regarding PC, PSA showed high specificity (97.4%) and high diagnostic accuracy (95.8%). AMACR showed a specificity of 73.7% for PC and diagnostic accuracy of 84.7%, but it was more sensitive compared with PSA and its results does not vary in high grades. Statistical analysis revealed that combined GATA3/AMACR panel has the best diagnostic characteristics.Conclusion
We concluded that the newly discovered marker GATA3 with AMACR are the best preliminary panel to be applied in the challenging cases of high-grade UC and PC.