NKX3.1 (EP356)

NKX3.1 is a prostate specific androgen-regulated homeobox gene located on chromosome 8.1,2,3 It is difficult to distinguish between high grade prostate adenocarcinoma and high grade infiltrating urothelial carcinoma using hematoxylin and eosin stained specimens.2 Current prostate adenocarcinoma markers such as PSA and PSAP are very useful in determining prostate origin of prostate cancer in other sites, but have lower sensitivity when identifying poorly differentiated compared to well differentiated cases.2 Currently, thrombomodulin and uroplakin are used to identify tumors of urothelial origin; however, their sensitivities are suboptimal.2 In a study by Gurel et al., nearly all cases of metastatic prostate adenocarcinoma were stained by NKX3.1.1 NKX3.1-positive prostate carcinoma cells exhibit nuclear staining.1In another study conducted by Chuang et al., nearly all cases of urothelial carcinoma were negative for NKX3.1.2 Lastly, NKX3.1 has also been found to be expressed in invasive ductal carcinomas (IDC) and invasive lobular carcinomas (ILC) of the breast.3 NKX3.1 expression is limited to ER, PR, and AR positive carcinomas and is more frequently expressed in ILC than IDC.3 NKX3.1 has a high specificity and sensitivity for prostate adenocarcinomas and can be used to help distinguish between prostate carcinoma and urothelial carcinomas.1,2