[974] The Spectrum of Morphologic Findings in Clear Cell Papillary Renal Cell Carcinoma.

Sean R Williamson, John N Eble, Liang Cheng, David J Grignon. Indiana University, Indianapolis

Background: Clear cell papillary renal cell carcinoma (CCPRCC) is an interesting renal neoplasm recently recognized in kidneys with and without end-stage renal disease (ESRD). Immunohistochemical (IHC) and molecular properties are distinct from clear cell and papillary RCC. The spectrum of morphologic features and prominence of the papillary component have not been well elucidated.
Design: We retrieved cases of CCPRCC from the authors' archives. Light microscopic features were evaluated and IHC was performed for CK7, CA-IX, CD10, AMACR, SMA, desmin, ER, and PR.
Results: We identified 23 tumors from 13 patients, 3 with ESRD (23%). Age ranged from 46 to 71 years (mean 58), with M:F ratio of 11:2. Tumor size ranged from 0.3 to 7.5 (mean 2.6) cm. The majority of cases were Fuhrman grade 2 (69%), while fewer were grade 1 (23%) or 3 (8%). Stage was predominantly pT1 (92%). In 77% of cases papillary architecture was limited to a minority of the tumor, some with only minute abortive papillae. Only 23% showed a majority of papillary architecture or large fields composed of branched papillae. All tumors showed gross or microscopic cystic spaces, some with prominent peripheral cysts. All were encapsulated. The majority showed secretory cells (85%) with nuclei aligned at the apical end of the cells, and all showed at least focal branched/stellate ductular structures. Calcification or ossification was present for 3 cases, and no case showed psammoma bodies or foamy macrophages within papillae. IHC demonstrated the typical profile for CCPRCC (CK7+, AMACR -, CD10 -, CA-IX+), with the following exceptions: 4 cases with weak CD10 membrane positivity in only the flattened cyst lining cells, and 1 case with weak AMACR staining. The stromal component demonstrated SMA positivity in all cases, with capsular desmin staining in only 3 cases. ER and PR were uniformly negative.
Conclusions: CCPRCC is a unique neoplasm that typically presents at low grade and stage. Although papillary architecture is characteristic, abundant extensively branched papillae are infrequent. Key features that suggest the diagnosis include a prominent, often peripheral cystic component, alignment of cell nuclei away from the basement membrane (secretory cells), and stellate ductular structures (similar in shape to benign prostatic acini). Some tumors may be nearly entirely cystic with only minute papillary structures. Tumor ossification or calcification can be seen. We have expanded the IHC profile of CCPRCC to include focal SMA positivity in the stromal component, lack of ER/PR expression in the stroma, and occasional positivity of the flattened cyst lining for CD10.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 84, Wednesday Morning

 

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