[1081] Decreased p63 Expression Is Common in Micropapillary Urothelial Carcinoma (MPUC) and High Grade Urothelial Carcinoma (HGUC)

Bing Zhu, Xiaoqi Lin, Stephen Rohan, Minghao Zhong, Rajen Goyal, Elizabeth Gersbach, Ximing Yang. Northwestern University, Chicago

Background: In normal human tissues strong nuclear p63 protein expression is present in the basal layer of stratified squamous and transitional epithelia. Immunohistochemistry (IHC) for p63 is frequently used in clinical practice to aid in diagnosing urothelial carcinoma (UC). However, loss of p63 expression has been described in high stage UC. Micropapillary urothelial carcinoma (MPUC) is a variant of bladder cancer with an aggressive behavior that frequently presents at an advanced stage. The aim of our study was to investigate p63 IHC in MPUC in comparison to conventional UC of different grades and stages.
Design: IHC for p63 expression was performed on paraffin embedded tissue sections of 23 cases of HGUC, 20 cases of low grade urothelial carcinoma (LGUC) and 20 cases of MPUC. IHC staining was scored semiquantitatively as follows: 0 (no reactivity); 1+ (< 10% cells labeling); 2+ (10 – 50% cells labeling); 3+ (50 – 75% positive); 4+ (75– 90% positive); and 5+ (> 90% positive). Only nuclear labeling was considered positive.
Results: p63 expression was identified in non-neoplastic surface urothelium in all MPUC cases, however, the MPUC tumor cells were negative for p63 (Table 1). 22% of high stage (pT2 or pT3) HGUC were also negative for p63. Additionally, 22% of pT2 or pT3 HGUC showed only 1+ labeling. In contrast, 60% of low stage (pTis or pT1) HGUC exhibited more than 3+ labeling. Finally, 70% of LGUC exhibited 5+ (more than 90% tumor cells) labeling for p63.

Table1. P63 staining in MPUC and HGUC
P63 stainingMPUC (n = 20)Conventional UC (n = 23)

Table 2. P63 staining in HGUC
% of tumor cellspTis (n = 2)pT1 (n = 3)pT2 (n = 15)pT3 (n = 3)Total (n = 23)percentage
< 10% positive0131521%
10-50% positive0131521%
50-70% positive0130417%
75-90% positive1011313%
> 90% positive101029%

Conclusions: Our study indicates that p63 IHC is negative in the majority of MPUC cases. Additionally, 44% of high stage (≥ pT2) HGUC exhibited no more than focal (<10% of cells) labeling for p63. All of our LGUCs were positive for p63. Our findings suggest that decreased p63 expression in UC is more common in tumors with aggressive features. Future studies evaluating the utility of p63 as a prognostic marker in UC are warranted.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 91, Tuesday Afternoon


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