[915] Differentiating Chromophobe Renal Cell Carcinoma from Oncocytomas: Utility of a Novel Immunomarker, Amylase 1A

Sarika Jain, Milon Amin, Somak Roy, Marie Acquafondata, William LaFramboise, Sheldon Bastacky, Rajiv Dhir, Anil Parwani. University of Pittsburgh Medical Center, Pittsburgh, PA

Background: Chromophobe renal cell carcinoma (Ch-RCC) and Oncocytoma are distinct renal tumors with a common origin: the intercalated cell of the collecting duct. Both tumors present with a perplexing overlap of morphological and immunohistochemical (IHC) features. Unfortunately, no biomarker specifically aids in this distinction; yet, distinction is needed because clinical outcomes are signficantly different. A recent study from our institution (Krill-Burger et al. Am J Pathol 2012;180:2427) demonstrated deletion in 1p21.1 region in Ch-RCCs. AMY1A as one of the genes in this region. Our aim was to assess the utility of AMY1A as a diagnostic biomarker for oncocytoma.
Design: IHC staining was performed on whole slide sections of 14 oncocytomas and 21 Ch-RCC using an anti-AMY1A antibody (Abnova, clone 2D4, monoclonal). Tissue microarrays (TMAs) consisting of oncocytoma (n=57), chromophobe RCC (n=9), normal kidney, and various other normal organs were also assessed by IHC. Staining was assessed using H-score method (stain intensity x percentage of cells positive for each intensity score). Staining intensity was graded as no staining=0, weak = 1, moderate=2 and strong =3.

Table 1: H-score of 71 oncocytoma and 30 Ch-RCC cases stained with Anti-AMY1A antibody
 AMY1A (Staining Intensity)
Oncocytoma (n=71)0 (0%)10 (14%)25 (35%)36 (51%)
Chromophobe RCC (n=30)25 (83%)5 (17%)0 (0%)0 (0%)

A total of 71 oncocytomas (57 TMA cores and 14 whole slides) and 30 Ch-RCC (9 TMA cores and 21 whole slides) were studied. All oncocytoma cases expressed AMY1A. 83% (25/30) Ch-RCC cases were negative for AMY1A stain. Only 5 out of 30 cases of Ch-RCC showed non-specific or very weak staining (mean H-score=54). Normal kidney cores showed a moderate to strong staining of the distal convoluted tubules.
Conclusions: Based on our study, strong, diffuse AMY1A can be used as a highly sensitive and specific marker for oncocytoma and can reliably distinguish an oncocytoma from a Ch-RCC.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 134, Monday Morning


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