NKX3.1 is a protein found in humans and is encoded by the NKX3.1 gene located on chromosome 8 (1). The homeodomain containing transcription factor NKX3A is a putative prostate tumor suppressor that is expressed in a largely prostate-specific and androgen-regulated manner. NKX3.1 protein has been found to be positive in the vast majority of primary prostatic adenocarcinomas (1). A recent study showed that NKX3.1 staining was highly sensitive and specific for highgrade prostatic adenocarcinomas (2). The sensitivity for identifying metastatic prostatic adenocarcinomas overall was 98.6% (68/69 cases positive) for NKX3.1, and 94.2% (65/69 cores positive) for PSA (2). The specificity of NKX3.1 was 99.7% (1/349) in various cancers (2). NKX3.1 stains nuclei in both normal and prostate cancer; thus providing a robust stain that is easy-to-interpret, similar to other transcription factors such as TTF-1 or CDX2 (2).