[993] Is Renal Angiomyoadenomatous Tumor (RAT) a New Entity? Clinicopathologic, Immunohistochemical and Molecular Cytogenetic Study of 3 Cases

Irene Rodriguez, Angel Panizo, Francisco J Queipo, Irene Amat, Maria R Mercado, Marisa Gomez, Javier Pardo. Complejo Hospitalario de Navarra "A", Pamplona, Spain; ClÍnica Universidad de Navarra, Pamplona, Spain

Background: Several low-grade renal cell tumors have been described. Recently, RAT (renal angiomyoadenomatous tumor), a tumor composed of admixture of an epithelial component and leiomyomatous stroma has also identified. The aim of this study is to investigate 3 new cases of RAT.
Design: We performed a detailed clinical, morphological, IHC, and molecular study. Copy numbers of chromosomes (CHRO) 7 and 17 were evaluated by automated dual-color silver-enhanced in situ hybridization. CHRO imbalance was defined on the basis of changes in both CHRO index and signal distribution. Sequencing of von Hippel-Lindau gene was also carried out.
Results: There were 2 female and 1 male patients; age ranging from 45 to 57 years, and the size from 0.7 to 2 cm. All 3 tumors were located in the right kidney (stage pT1a). One patient had a history of von Hippel Lindau disease (VHLD). None had signs of tuberous sclerosis. All patients remain alive and free of recurrent or metastases after median follow-up of 5 months (range 1-25.5 months). Grossly the tumors were solid, well-defined, and grayish. Tumors were composed of admixture of epithelial cells with clear cytoplasm and prominent smooth muscle-rich stroma. Epithelial cells formed tubules or tubulopapillary structures endowed with blister-like cytoplasmic processes. All tubular structures were lined and surrounded by fine capillary network. Prominent benign leiomyomatous stroma was present in all cases. Perirenal, renal sinus, vascular invasion, tumor necrosis, and sarcomatoid dedifferentiation were not observed. All cases were positive for CK7, HMCK, CK19, EMA, PAX8, and CD10. Stromal component was positive for SMA, desmin, and h-caldesmon. CD34 and CD31 highlighted a rich capillary network surrounding the epithelial component. No positivity was observed for AMACR, RCC, TFE3, HMB45, and S100. All cases were diploid for CHRO 17 and 7 and 1 showed a trend towards polysomy of CHRO 7 by SISH. 1 tumor showed mutation in the VHL gene (patient with VHLD).
Conclusions: RAT appears most likely a distinct entity based on their morphologic, IHC, and molecular features. The association of the epithelial component with the capillary network is unique and can serve as a diagnostic clue. The immunophenotype (CK7+, CK19+, HMCK+, RCC-, AMACR-) is sufficiently distinct to allow easy separation from ccRCC and pRCC. Our findings suggest that RAT may be biologically indolent tumors with absence of distant metastases and sarcomatoid transformation.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 100, Wednesday Morning


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