[813] Atypical Renal Cysts: A Clinicopathologic Study of 33 Cases

YB Chen, JI Epstein. The Johns Hopkins Hospital, Baltimore

Background: Renal cysts with more complex architectural patterns than a simple flat lining are infrequently encountered and have typically been reported in association with renal cell carcinoma (RCC), end-stage renal disease (ESRD), autosomal dominant polycystic kidney disease (ADPKD), and von Hippel-Lindau syndrome (VHL). The morphology and prognosis of these cystic lesion, especially outside of these settings have not been well characterized.
Design: We identified 33 cases (15 sent in consultation) with atypical renal cysts (1993-2009).
Results: All Patients: There were 24 males and 9 females ranging in age from 34 to 85 years old (median 56). Concurrent renal diseases included RCC 12/33 (36%) (7 clear cell, 5 papillary), ADPKD 4/33 (12%), ESRD other than due to ADPKD 6/33 (18%), calculi 3/33 (9%), and oncocytoma 1/33 (1 patient with RCC had VHL; 2 RCCs developed in patients with ESRD). The other 9 (27%) patients had no known renal abnormalities besides the cysts. Because RCC, ADPKD and ESRD significantly impacts prognosis and these diseases have been reported to be associated with atypical cysts, we focused on the remaining 13 (39%) patients. Cases without RCC, ADPKD, ESRD: There were 9 males and 4 females, ages 34-80. On imaging, the cysts ranged from 0.8 to 6.5 cm, Bosniak grade 2-3; at least 5 appeared to be multiloculated complex cysts. 5 patients had additional smaller cysts in the ipsilateral or contralateral kidney. The epithelial lining in atypical cysts either contained: 1) areas of papillary hyperplasia with single or multiple layers of cuboidal cells with either hobnail or clear cell features; or 2) layers of stratified cells with eosinophilic or clear cytoplasm. No mitoses or prominent atypia were present. Proteinaceous material and in rare cases hemorrhage were seen within the cyst lumen. In contrast to multiloculated cystic RCC, there were no mural nodules of clear cells. The histologic features of atypical cysts in cases associated with RCC, ADPKD and ESRD were similar to that observed in isolated atypical cysts. Treatment included cyst resection (n=3), partial nephrectomy (n=4) and nephrectomy (n=6). Among 8 patients with follow-up information (mean 46 months, range 3-113), 1 died of metastatic lung cancer, yet the other 7 patients were well with no additional renal tumor or cyst development.
Conclusions: Atypical renal cysts clinically often present as complex cysts suspicous for cystic RCC. Atypical cysts as isolated findings appear to have a low-risk of recurrence or malignant transformation. It is critical to distinguish them from multiloculated cystic RCC.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 160, Tuesday Morning


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