[923] Immunohistochemical Expression of OCT 3/4 in Renal Medullary Carcinoma – A Potential Diagnostic Pitfall.

Priya Rao, Pheroze Tamboli. University of Texas MD Anderson Cancer Center, Houston

Background: Renal medullary carcinoma (RMC) is a rare aggressive renal tumor that classically afflicts young men with sickle cell trait. The tumor shows overlapping pathologic & clinical characteristics with collecting duct carcinoma (CDC) & urothelial carcinoma (UC) which often results in a diagnostic conundrum. When the tumor presents in a metastatic site in the absence of a history of a renal tumor, germ cell tumor (GCT) is a diagnostic consideration given the young age of most patients (pts). OCT3/4 is an immunohistochemical marker that is routinely used in clinical practice & is widely considered to be a specific marker for GCT. Although OCT3 gene expression has been previously reported in the mammalian kidney the immunohistochemical expression of OCT3/4 in renal tumors has not been studied.
Design: We studied the pathologic & immunohistochemical characteristics of 12 RMCs. Immunohistochemical stains for OCT3/4, Ulex Europeaus lectin, CK7, PIN dual, PAX8 & PAX2 were performed & the expression of these same markers were compared in a group of 5 CDCs & 10 UCs
Results: Pts with RMC ranged in age from 21- 39 yrs (mean 31.8). All had sickle cell trait. There were 8 men & 4 women. Tumor size ranged from 3.8-17.5 cm (mean 8.1 mos). OCT3/4 staining was noted in 8/12 RMC's & was absent in all cases of CDC & UC. 7/12 RMC cases also stained for Ulex Europaeus lectin. Interestingly all but 1 case of CDC were negative for this marker. The immunohistochemical results are summarized below.

Distribution of positive immunohistochemical stains in RMC, CDC & UC.

	OCT3/4	Ulex Europaeus	Vimentin	CK7	PINdual	PAX8	PAX2
RMC	8/12	7/11	8/12	9/12	4/12	9/10	7/11
CDC	0/5	1/5	NA	0/5	0/5	3/5	NA
UC	0/10	1/10	0/10	7/10	7/10	0/10	0/10

NA- Not available

Follow up was available in all cases (range 3-24 mos). 7/12 pts were DOD (mean time to death 12.5 mos) & 5 pts were AWD (mean FU 7.6 mos).
Conclusions: OCT3/4 expression is not specific for GCT & may be noted in a subset of RMC's. Caution must be employed in interpreting the presence of OCT3/4 staining in a poorly differentiated neoplasm at a metastatic site as a GCT, especially when a clear history of sickle cell trait is not available as this may represent a potential diagnostic pitfall. The expression of OCT3/4 may have a role in discriminating RMC from CDC & UC however further studies with a larger number of cases are required to establish the utility of this marker in routine clinical practice.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 110, Wednesday Morning