Cystic Nephroma

Juan E Small, MD - Case Coordinator
Teddy Jinnteh Su, MD - Radiology Discussion
Xuefei Hong, MD - Pathology Discussion
Kemal Tuncali, MD - Attending Radiologist
Steven E Seltzer, MD - Attending Radiologist
Pablo R Ros, MD, MPH - Attending Radiologist

August 11, 2003

Presentation

Imaging Findings

Axial CT images show a heterogeneous (predominantly hypodense) mass in the interpolar region of the left kidney. The right kidney appears to be normal. The low density suggests the possibility that the mass may contain fat, which would indicate a benign angiomyolipoma. The more likely entities on the differential diagnosis are renal cell carcinoma, metastasis, and lymphoma. The apparent heterogeneity may also indicate that the mass is cystic, with enhancing septations.

Axial and coronal T2-weighted MR images show a polycystic mass with high signal throughout. Linear low-signal areas most likely represent septations.

Differential Diagnosis

Diagnosis

Discussion

The nephrectomy sample contains a 4.5-cm multilocular cyst in the hilum. The cyst is circumscribed and surrounded by a fibrous capsule. The loculi are filled with a clear, pale yellow fluid. There are no solid components. Low power microscopy illustrates the multilocular cysts separated by fibrous tissue. At higher power, both fibrous tissue and flattened lining cells are visible. In some areas, it is possible to see the hobnailed configuration of the lining cells. There is no collection of epithelial cells with clear cytoplasm, as would characterize renal cell carcinoma. The vascular and ureteral margins are free of tumor. The non-neoplastic renal parenchyma demonstrates mild glomerulosclerosis, mild interstitial chronic inflammation and minimal arteriolosclerosis.

Radiology Discussion:

Cystic nephroma, also known as multilocular cystic nephroma, is an uncommon neoplasm whose cause is unknown. There is no hereditary pattern. The epidemiology is bimodal in terms of both age and gender; the condition most often affects young boys (3 months - 4 years) and older women (>30 years). The manifestation is typically a unilateral and solitary multiloculated cyst. The various cysts are noncommunicating, lined with epithelial cells, and separated by fibrous septa. There is no renal parenchyma within the cyst and no connection to the collecting system, although the cyst can herniate into the renal pelvis, which is a pathognomonic finding. The uninvolved kidney is generally normal.

Cystic nephroma typically presents as a painless abdominal mass without systemic symptoms. The appearance on CT is a multiloculated cystic mass; the septa usually do not enhance and are sometimes calcified (10%). Hydronephrosis may be seen, as the mass may compress the collecting system. Cystic renal cell carcinoma can look similar, but will usually have enhancing nodular and thick septa

'Multilocular cystic renal tumor' is a term that includes two histologically distinct entities: cystic nephroma and cystic partially differentiated nephroblastoma (CPDN). In these tumors, the septa are the only solid components and both are benign. It has been suggested that there may be a spectrum connecting cystic nephroma, CPDN, and Wilm's tumor (in children, the preoperative diagnosis for a multilocular cystic renal tumor is often Wilm's tumor). Cystic nephroma can appear identical to CPDN on imaging and gross pathology; the only difference is that the septa in cystic nephroma do not contain blastemal cells (these cells are a distinguishing characteristic of CPDN).

References

Lowe L, et al. Pediatric Renal Masses: Wilms Tumor and Beyond. Radiographics 2000; 20:1585-1603

www.amershamhealth.com/medcyclopaedia

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