Hawari R, Fernandes L, Park KJ, et al. - Variable, and often focal, immunohistochemical expression with traditional prostatic markers [prostate-specific antigen and prostatic acid phosphatase (PSAP)] are identified in cervical ectopic prostatic tissue and vaginal tubulosquamous polyp. Periurethral Skene’s glands, the female equivalent of prostatic glands in the male are thought to be the origin of these rare lesions. Studies have described expression of the prostatic marker NKX3.1 in ectopic prostatic tissue and tubulosquamous polyp but no studies have examined immunoreactivity with this marker in adenoid basal carcinoma, a rare and indolent cervical neoplasm. Nineteen cases [adenoid basal carcinoma (n = 6), cervical ectopic prostatic tissue (n = 11), and vaginal tubulosquamous polyp (n = 3); 1 case contained both adenoid basal carcinoma and ectopic prostatic tissue] were stained with NKX3.1. In all cases, diffuse nuclear immunoreactivity was identified in the glandular component of these lesions while normal endocervical glands were negative. Although further studies are required to determine the specificity of NKX3.1, positivity with this marker may be valuable in diagnosing these uncommon lesions. Compared with traditional prostatic markers, NKX3.1 is identified to be a more sensitive marker of ectopic prostatic tissue and tubulosquamous polyp; positive staining yields further support that these lesions show “prostatic” differentiation and are of Skene’s gland origin. In adenoid basal carcinoma, NKX3.1 and PSAP positivity raises the possibility of a correlation with benign glandular lesions showing prostatic differentiation.