[816] Utility of Gata3 and Pax8 Immunohistochemistry in Diagnosing Sarcomatoid Urothelial Carcinoma (UC) and Sarcomatoid Renal Cell Carcinoma (RCC)

Alex Chang, Fadi Brimo, Elizabeth A Montgomery, Jonathan I Epstein. The Johns Hopkins Hospital, Baltimore

Background: PAX8 is a sensitive maker for RCC. GATA3 is a newly described marker for UC. Both have not been studied in their ability to distinguish sarcomatoid RCC from sarcomatoid UC from other spindle cell lesions seen in the GU tract.
Design: TMAs were constructed from 45 cases of sarcomatoid RCC, 46 cases of sarcomatoid UC, and compared to an existing TMA of 161 primary sarcomas. In addition, sections from 10 sarcomatoid UCs involving the upper urinary tract, 13 atypical epithelial angiomyolipomas (AMLs) of the kidney, 12 inflammatory myofibroblastic tumors (IMTs) and 4 leiomyosarcomas (LMSs) involving the bladder were studied. Only moderate or strong staining was considered positive.

 PAX8 (+)GATA3 (+)PAX2 (+)RCC (+)CD10 (+)
Sarcomatoid RCC31/45 (69%)0/45 (0%)3/45 (7%)2/45 (4%)23/45 (51%)

 PAX8 (+)GATA3 (+)Thrombomodulin (+)
Bladder Sarcomatoid UC3/46 (7%)14/46 (30%)9/46 (20%)

Of 10 cases of sarcomatoid UC of the upper urinary tract, 1 (10%) was positive for PAX8 and 2/10 (20%) were positive for GATA3. Of the 161 primary sarcomas, none of the cases that would be considered in the differential diagnosis of sarcomatoid RCC or UC were positive for either PAX8 or GATA3 (only 1 positive EWINGS/PNET for PAX8). None of the renal 13 atypical epithelioid AMLs were PAX8 positive, and all of the IMTs and LMSs of the bladder were GATA3 negative. Of the 17 cases of sarcomatoid RCC with an epithelial component present for examination (10 clear cell, 2 chromophobe, 2 papillary, and 2 unclassified), 15 (88%) were PAX8 positive, and of those 15, 10 (67%) retained PAX8 staining in the sarcomatoid areas. Of the 19 sarcomatoid UC with an epithelial component available for examination (7 invasive high grade UC, 11 high grade papillary non-invasive carcinomas, and 1 CIS), 14 (74%) were GATA3 positive, and of those cases, 6 (43%) retained GATA3 staining in the sarcomatoid areas.
Conclusions: PAX8 is the most sensitive marker for sarcomatoid RCC. While PAX8 can be utilized to exclude atypical epithelioid AMLs and sarcomas with high grade and spindle cell morphology, sarcomatoid UC may also be PAX8 positive limiting its utility. GATA3 is a specific marker for sarcomatoid UC and can be used to exclude sarcomatoid RCC and other spindle cell lesions, although its sensitivity in sarcomatoid UC is not high. Focal weak nonspecific nuclear staining was seen in a few cases with both PAX8 and GATA3, such that only moderate-strong nuclear staining should be considered positive.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 87, Tuesday Afternoon


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