[1003] Clear Cell Papillary Renal Cell Carcinoma: An Immunohistochemical Study

Michelle R Pramick, Amy Ziober, Zhanyong Bing. Hospital of the University of Pennsylvania, Philadelphia, PA

Background: Clear cell papillary renal cell carcinoma (CCPRCC) is a recently described low-grade renal cell tumor. This unique type of tumor can occur in both end-stage and normal kidneys. Histologically, this tumor can display various architectural patterns, with cells that have clear cytoplasm and low Fuhrman nuclear grade. Available data suggest that this tumor is not aggressive and patients with this type of tumor have a good prognosis. PAX-8 is a member of the PAX family of transcription factors, which plays an important role in regulating cell proliferation, differentiation, apoptosis, migration, and stem-cell maintenance. It is involved in the normal development of renal, thyroid, and Müllerian tissues. PAX-8 has been shown to be specifically expressed in tumors of thyroid, Müllerian and renal origin. Expression of PAX8 has been demonstrated in major renal epithelial neoplasms and is a useful marker in determining the primary origin of a neoplasm. No previous study has been done to investigate the expression of this marker in CCPRCC.
Design: In this study, we investigated the expression of PAX-8, carbonic anhydrase IX (CA IX), CK7, and Alpha-methylacyl-CoA-racemase (AMACR) in this tumor by immunohistochemistry in a group of 20 cases of CCPRCC.
Results: The twenty cases of CCPRCC had the following demographics: 8 female and 12 male patients; 13 left, 5 right, 2 bilateral; 5 cystic. The tumors ranged in size from 0.3 to 7.2 cm with an average of 1.9 +/- 1.4 cm. Each case represented a stage I tumor with low Fuhrman grade (9 Fuhrman grade 1 and 11 Fuhrman grade 2). The background renal parenchyma showed end-stage changes in 5 cases; the remainder had no specific pathologic changes. CCPRCC showed intermediate or diffuse nuclear positivity for PAX-8 in each case, with predominantly moderate intensity. Ninety percent of the cases showed some degree of cytoplasmic staining for CA IX, predominantly with moderate intensity. In addition, each case of CCPRCC showed diffuse strong membranous staining for CK7. The majority of CCPRCCs (95%) were negative for AMACR.
Conclusions: PAX-8, CA IX, CK7, and AMACR comprise a concise panel for distinguishing CCPRCC from its mimics. PAX-8 positivity helps to confirm the renal origin of this tumor. Positivity for CA IX and CK7 differentiate CCPRCC from conventional clear cell renal cell carcinoma, which is usually CA IX positive while CK7 negative. The CK7 positive and AMACR negative pattern seen in CCPRCC differentiates it from papillary renal cell carcinoma, which is usually positive for both AMACR and CK7.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 151, Monday Morning


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