[1014] The Value of Napsin A in the Work-Up of Renal Neoplasms

Allan R Smith, Shweta Patel, Jan F Silverman. Allegheny General Hospital, Pittsburgh, PA

Background: Napsin A is an aspartate protease that is expressed in the cytoplasm of normal renal, thyroid and lung epithelium and has proven utility in the diagnosis of pulmonary adenocarcinomas. PAX 8 is a transcription factor seen in tissues of Mullerian, renal and thyroid origin and is used in the evaluation of adenocarcinomas of unknown primary origin. While the PAX family of transcription factors including PAX 8 have been well studied, there are no studies discussing the combined utility of PAX 8 and Napsin A in the evaluation of renal neoplasms. Additionally, there are only two discordant studies evaluating the application of Napsin A in a limited spectrum of renal neoplasms. Therefore, we evaluated the utility of immunohistochemistry (IHC) for Napsin A and PAX 8 in a spectrum of renal neoplasms.
Design: Napsin A and PAX 8 were applied to archived tissue from various renal neoplasms. Reactivity was scored in a four tiered manner with positive results defined as scores of 1 (< 25 % of cells staining with minimal intensity), 2 (moderately intense staining in 25 – 50 % of the cells) and 3 (strong staining in > 50 % of the cells). Internal positive and negative controls were present in the surrounding normal renal tissue of each specimen chosen. The classification of each renal neoplasm was established by histologic and IHC studies. A Fischer test using Graphpad Prism software was used for statistical analysis.

Renal NeoplasmNapsin A # positive (% positive)
clear cell RCC5/20 (25%)
papillary RCC15/18 (83%)
chromophobe RCC1/11 (9%)
oncocytoma7/7 (100%)

Napsin A distinguishes papillary renal cell carcinoma (RCC) from clear cell RCC (p< 0.05; p= 0.0004), and chromophobe RCC from oncocytoma (p< 0.05; p= 0.0003). Napsin A reactivity was also seen in 1 of 2 collecting duct carcinomas, 1 of 2 multicystic RCC and 0 of 1 metanephric adenomas. All of the renal neoplasms examined were reactive for PAX 8.
Conclusions: Napsin A can be a useful discriminator between oncocytoma and chromophobe RCC and papillary versus conventional RCC, especially in the work-up of core needle biopsies of oncocytic renal neoplasms or problematic resected cases. Consistent with previous literature, Napsin A is also useful in an IHC panel that includes CK 7 for the identification of papillary RCC. PAX 8 did not contribute to the classification of renal neoplasms.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 150, Tuesday Morning


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