GATA3 expression in paragangliomas: a pitfall potentially leading to misdiagnosis of urothelial carcinoma.

GATA3 is a zinc-finger transcription factor, which is expressed in various normal and neoplastic tissues. Amongst tumors, it labels urothelial carcinoma, collecting duct carcinoma of the kidney, breast carcinoma, lymphoma and, uncommonly, endometrial carcinoma. Few studies have investigated its positivity in various neoplasms that may mimic urothelial neoplasms. In this study, we evaluated GATA3 expression in urinary bladder paragangliomas, which may closely mimic urothelial carcinomas. We retrieved 12 cases of paragangliomas from the urinary bladder and 20 cases of paragangliomas from non-urologic sites using the Hopkins Pathology Data Base system. GATA3 was positive in 10 of the 12 (83%) urinary bladder paragangliomas studied on routine slide sections. Most (6/12) of the staining was diffusely strong (3+) staining, whereas the rest (4/12) that were positive showed mixed intensities (strong 3+ to moderate 2+). The 20 paragangliomas from other sites were constructed into tissue microarrays, wherein three cores from each tumor were taken. Fifteen out of 20 (75%) paragangliomas outside of the bladder were positive for GATA3 staining. Moderate (2+) or strong (3+) staining was seen in 13/20 (65%) of extravesical paragangliomas, ranging from 5 to 100% of the cell labeling (mean 59%, median 60%). In the remaining 7/20 (35%) cases, only weak (2/7) or negative (5/7) immunoreactivity for GATA3 was seen. An additional 15 cases of metastatic paraganglioma from various primary sites were retrieved with 12 of 15 (80%) metastatic paragangliomas staining positively for GATA3. Overall, for paragangliomas, regardless of site, 78.7% were positive for GATA3. Recognition of this finding will aid pathologists in preventing a misdiagnosis of a urothelial tumor based on GATA3 expression, which is critical given the differences in treatment, follow-up and prognosis between bladder paragangliomas and urothelial carcinoma.