Immunohistochemical profile of the penile urethra and differential expression of GATA3 in urothelial versus squamous cell carcinomas of the penile urethra

The penile urethra has a distinctive morphology not yet fully characterized by immunohistochemistry. In addition, both urothelial and squamous cell carcinomas have been reported in the penile urethra, and the distinction between these 2 tumors might be difficult. The purposes of this study are to assess the histology and immunohistochemical profile (CK20, CK7, p63, and GATA3) of the penile urethra and to assess the usefulness of Trans-acting T-cell-specific transcription factor (GATA3) and human papillomavirus detection in distinguishing urothelial versus squamous cell carcinomas. Normal penile urethra was evaluated in 11 total penectomies. The penile urethra was lined by 2 cell layers: a superficial single layer of CK7+, CK20-, and p63- columnar cells and a deep stratified layer of CK7-, CK20-, and p63+ cubical cells. Both layers were GATA3+, supporting urothelial differentiation. In addition, 2 tissue microarrays and 6 surgical specimens of primary tumors of the penile urethra (3 urothelial and 3 squamous cell carcinomas) were evaluated for GATA3 expression. In the tissue microarrays, 22 of 25 upper tract urothelial carcinomas and 0 of 38 penile squamous cell carcinomas were GATA3+. In the surgical specimens, GATA3 was positive in all urothelial carcinomas and negative in all squamous cell carcinomas. Human papillomavirus was detected in 2 of 3 squamous cell carcinomas and in 0 of 3 of the urothelial carcinomas. In conclusion, the penile urethra is covered by epithelial cells that are unique in morphology and immunohistochemical profile. In addition, our study suggests that GATA3 and human papillomavirus detection are useful markers for distinguishing urothelial carcinomas from squamous cell carcinomas of the penile urethra.