GATA3 Positivity in Benign Radiated Prostate Glands: A Potential Diagnostic Pitfall

Histologic changes following radiation therapy to the prostate include multilayering of glands, atrophy, squamous metaplasia, and often marked random nuclear atypia. We have seen multiple consultation cases where the differential diagnosis of these radiated prostate glands included urothelial carcinoma, with multilayered to solid-appearing proliferations that were positive by immunohistochemistry for GATA3. To formally investigate this issue, 30 cases of benign prostate tissue with radiation atypia, from 1990 to 2015, were obtained from our institution. Cases were evaluated by immunohistochemistry for the prostate-specific markers prostate-specific antigen (PSA), P501S (Prostein), and NKX3.1 and urothelial markers GATA3 and uroplakin 2. GATA3 was positive in 100% of cases, with 70% showing moderately strong to strong staining in a mostly patchy manner within a gland. PSA was positive in 93.3% of cases, with 89.2% showing moderately strong to strong staining in a mostly diffuse manner. P501S was positive in 96.7% of cases, with 93.1% showing moderately strong to strong staining in a mostly patchy manner. NKX3.1 was positive in 82.8% of cases, with 33.3% showing moderately strong to strong staining in a mostly patchy manner. Uroplakin 2 was negative in 100% of cases. Our findings highlight that GATA3 is often positive in benign prostate glands with radiation atypia, which along with the morphologic features present a pitfall for the misdiagnosis of urothelial carcinoma. A combination of PSA and P501S is the best prostate-specific panel for use in radiated prostate, with the caveat that they are often patchy and do not stain all radiated glands.