DOI: 10.1148/rg.284075184
RadioGraphics 2008;28:1221-1225
© RSNA, 2008
Best Cases from the AFIP
Multilocular Cystic Renal Tumor: Cystic Nephroma1
Ian M. F. Silver, MD,
Alexander H. Boag, MD, and
Donald A. Soboleski, MD
1 From the Departments of Diagnostic Radiology (I.M.F.S., D.A.S.) and Pathology and Molecular Medicine (A.H.B.), Kingston General Hospital, Queen’s University, 76 Stuart St, Kingston, ON, Canada K7L 2V7. Received September 10, 2007; revision requested September 18 and received October 22; accepted October 23. All authors have no financial relationships to disclose.
Address correspondence to I.M.F.S. (e-mail: isilver3{at}cogeco.ca).
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History
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A 16-month-old girl was brought to the emergency department by her parents because of a large mass on the left side of her abdomen and increasing abdominal girth over a period of several months. The patient had no history of fever, weight loss, anorexia, or symptoms of urinary tract infection. She had been having normal bowel movements, and her energy levels were also normal. Her medical history was unremarkable. A large, hard, nontender left abdominal mass was felt at physical examination. Results of initial laboratory investigations revealed a urinary tract infection.
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Imaging Findings
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Radiography helped confirm the presence of a large, left-sided abdominal mass that was displacing and effacing adjacent bowel loops (Fig 1). No abnormal calcifications were seen. Subsequent ultrasonography (US) (Fig 2) revealed a large, multicystic left abdominal mass that was inseparable from renal parenchyma and was associated with moderate left pelvicaliceal dilatation. There was also mobile debris noted within the urinary bladder. Contrast material–enhanced computed tomography (CT) of the chest, abdomen, and pelvis was then performed; results confirmed the presence of a roughly 12.5 x 10.8-cm multilocular cystic mass arising from the left kidney (Fig 3). The mass extended into the renal pelvicaliceal collecting system, and moderate associated dilatation of the renal collecting system was seen. The mass also appeared to extend into the posterior pararenal space medially, with stranding observed in adjacent fat. No lymphadenopathy was seen. The mass was separate from the left adrenal gland, and no accumulation of contrast agent was seen within the mass on delayed images.
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Figure 1. Radiograph of the abdomen demonstrates a large soft-tissue–density mass occupying the left side of the abdomen, extending across the midline, and displacing and effacing adjacent bowel loops.
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Figure 2a. (a) Sagittal US image of the left renal fossa demonstrates a multicystic mass with variably sized cystic components and thin echogenic septa. (b) Sagittal US image shows the mass extending into the left renal pelvis (arrows).
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Figure 2b. (a) Sagittal US image of the left renal fossa demonstrates a multicystic mass with variably sized cystic components and thin echogenic septa. (b) Sagittal US image shows the mass extending into the left renal pelvis (arrows).
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Figure 3a. (a) Axial enhanced CT image shows a large, low-attenuation mass with multiple thin septations arising from the left kidney. The mass extends into the renal pelvis (black arrow). Residual normal renal parenchyma is seen (white arrow), and there is a thin claw of renal parenchyma extending around part of the mass (arrowheads). (b) Coronal oblique reformatted CT image better demonstrates the mass extending into the dilated renal collecting system and renal pelvis (arrow).
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Figure 3b. (a) Axial enhanced CT image shows a large, low-attenuation mass with multiple thin septations arising from the left kidney. The mass extends into the renal pelvis (black arrow). Residual normal renal parenchyma is seen (white arrow), and there is a thin claw of renal parenchyma extending around part of the mass (arrowheads). (b) Coronal oblique reformatted CT image better demonstrates the mass extending into the dilated renal collecting system and renal pelvis (arrow).
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Pathologic Evaluation
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The patient underwent open radical nephrectomy of the left kidney, with retroperitoneal lymph node resection and sparing of the adrenal gland. The resected kidney and mass, six left infrarenal paraaortic lymph nodes, and one left renal paraaortic lymph node were sent to the pathology department for further characterization. The tumor appeared well-circumscribed and multicystic, with focal necrotic areas, at gross examination. It was contained within a capsule, involved the renal cortex and the medulla, and extended into the renal pelvicaliceal collecting system. Mild dilatation of the proximal ureter was seen (Fig 4). No renal vascular invasion was identified.
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Figure 4. Photograph of the cut surface of the resected left kidney and mass shows multiple smooth-walled cysts separated by thin translucent septa. A portion of the mass has prolapsed into the renal pelvis (white arrows). Note the residual normal renal parenchyma (yellow arrow) and the claw sign (arrowheads). Scale is in centimeters.
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Microscopic examination of multiple sections of the tumor revealed numerous variably sized cysts that were lined by flattened to hobnail-shaped eosinophilic cells with minimal cytologic atypia seen (Fig 5). The stroma of the septa contained somewhat edematous collagenous tissue with cytologically bland spindle cells and chronic inflammatory cells. Scattered tubules were also present. No blastemal or nephronic tissue was seen within the septa, and no extension through the renal capsule or into the renal sinus fat was identified, despite the apparent extension that was seen at CT. The surgical report described dense adhesions between the mesocolon and Gerota fascia; the normal fascial planes were obliterated, which perhaps accounts for the imaging findings. It is not clear if obliteration of the fascial planes represents a type of desmoplastic reaction to the mass or if it is unrelated. There was no microscopic evidence of lymphatic or vascular invasion. Focal areas of coagulative-type necrosis were present, particularly in sections obtained from where the mass had pushed into the renal pelvis. No nephrogenic rests were found within the adjacent normal renal parenchyma, and the resected paraaortic lymph nodes were negative for neoplasia. The pathologic findings were diagnostic of cystic nephroma.
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Figure 5a. (a) Photomicrograph (original magnification, x20; hematoxylin-phloxin-saffron [HPS] stain) shows the edge of the multicystic mass (arrowhead) and adjacent compressed renal parenchyma (arrow). (b) Photomicrograph (original magnification, x40; HPS stain) shows multiple variably sized cysts that contain clear fluid and are separated by paucicellular fibrous septa. (c) Photomicrograph (original magnification, x200; HPS stain) demonstrates cysts that are lined by a single layer of benign, flattened to hobnail-shaped epithelial cells.
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Figure 5b. (a) Photomicrograph (original magnification, x20; hematoxylin-phloxin-saffron [HPS] stain) shows the edge of the multicystic mass (arrowhead) and adjacent compressed renal parenchyma (arrow). (b) Photomicrograph (original magnification, x40; HPS stain) shows multiple variably sized cysts that contain clear fluid and are separated by paucicellular fibrous septa. (c) Photomicrograph (original magnification, x200; HPS stain) demonstrates cysts that are lined by a single layer of benign, flattened to hobnail-shaped epithelial cells.
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Figure 5c. (a) Photomicrograph (original magnification, x20; hematoxylin-phloxin-saffron [HPS] stain) shows the edge of the multicystic mass (arrowhead) and adjacent compressed renal parenchyma (arrow). (b) Photomicrograph (original magnification, x40; HPS stain) shows multiple variably sized cysts that contain clear fluid and are separated by paucicellular fibrous septa. (c) Photomicrograph (original magnification, x200; HPS stain) demonstrates cysts that are lined by a single layer of benign, flattened to hobnail-shaped epithelial cells.
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Discussion
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Cystic nephroma is a rare, nonhereditary benign renal neoplasm that is purely cystic and is lined by an epithelium and fibrous septa that contain mature tubules (1,2). Cystic nephroma represents one end of a spectrum. At the other end of this spectrum is cystic partially differentiated nephroblastoma (CPDN), in which the septa contain foci of blastemal cells. Cystic nephroma and CPDN are indistinguishable from one another based on their gross and radiographic appearances (3) and can be lumped under the term multilocular cystic renal tumor (MCRT) (4).
MCRT was first described in the late 19th century as cystic adenoma. It has been given numerous names since then, including benign multilocular cystic nephroma, polycystic nephroblastoma, well-differentiated polycystic Wilms tumor, Perlman tumor, and differentiated nephroblastoma (5,6). The first CT images of MCRT were published in 1981 (7).
MCRT has a bimodal age and sex distribution and tends to occur in children (mostly boys with CPDN) between 3 months and 4 years of age and in adults (mostly women with cystic nephroma) between 40 and 60 years of age (4,8,9). MCRT is usually solitary, but bilateral tumors have been described (10). Recent evidence suggests that in the adult population, tumors that were initially diagnosed as cystic nephroma actually represent a genetically and histologically distinct entity called mixed epithelial and stromal tumor of the kidney (11,12). Some authors have proposed that cystic nephroma and mixed epithelial and stromal tumor of the kidney represent a spectrum of the same entity (12); however, further studies are needed to challenge this hypothesis. To our knowledge, no imaging features have been described in the literature to date that can be used to distinguish these tumors.
The clinical manifestation of MCRT varies. It most frequently manifests in children as a painless abdominal mass (9); hematuria and urinary tract infection are less common in children. Adults are more likely to present with abdominal pain or hematuria, whereas a painless mass, urinary tract infection, or hypertension are less common manifestations among adults (9).
At gross inspection, MCRT is a well-circumscribed mass with a thick fibrous capsule that contains multiple, fluid-filled, noncommunicating loculi separated by thin translucent septa. At microscopic examination, the septa are lined by flattened or cuboidal epithelia, with areas of eosinophilic cuboidal cells protruding into the lumen that produce a hobnail or teardrop appearance (9). Mature renal tubules may be seen within the septa. Unlike CPDN, cystic nephroma does not contain blastemal cells within the septa (13).
US is often the initial modality used to evaluate abdominal masses, particularly with pediatric patients. However, large masses may be evident on radiographs, as in our case. Radiography may also show calcifications, which are uncommon in MCRT. In the series by Madewell et al (9), only three of 57 patients (5%) had calcifications that were visible on radiographs. These calcifications were small curvilinear densities (9). At US, cystic nephroma typically appears as a renal multicystic mass with no solid or nodular elements. A claw or beak shape of adjacent normal renal parenchyma helps confirm the renal origin of the mass. Associated urinary tract obstruction may be evident, and very small loculi may mimic solid components because of their innumerable, closely packed acoustic interfaces (6,14). The loculi can range in size from microscopic to 4 cm in diameter (6,15).
At CT, cystic nephroma typically appears as a well-circumscribed, encapsulated multicystic mass with variably enhancing septa and no excretion of contrast agent into the loculi. The contents of the cyst may have similar or slightly higher attenuation than that of water, and if the cystic spaces are very small, the closely packed septa can mimic a solid mass (9). Extension into the renal pelvis and ureter may also be easily seen at CT.
The appearance of MCRT on magnetic resonance (MR) images has been described in several case reports. A multicystic mass with a capsule and septa that are hypointense regardless of pulse sequence is typical, presumably because of the fibrous tissue present in these structures. Contents of the cyst are hyperintense on T2-weighted images; their signal intensity varies on T1-weighted images, possibly because of the different concentrations of old hemorrhage or protein. The septa have also been shown to enhance on MR images following administration of gadolinium (16–18).
Although renal scintigraphy has been described in the work-up of MCRT (9), it presently has no diagnostic role.
The differential diagnosis of a pediatric multilocular renal mass includes cystic nephroma; cystic Wilms tumor or renal cell carcinoma; clear cell sarcoma; cystic variants of mesoblastic nephroma; and multicystic dysplastic kidney, especially the segmental form. The presence of solid components should discourage a diagnosis of cystic nephroma. Cystic nephroma has not been described either in the antenatal or neonatal periods, which should help to differentiate it from other tumors such as cystic mesoblastic nephroma (19). On CT images, visualizing the symmetric excretion of contrast material by the remaining functioning renal parenchyma helps to differentiate MCRT from multicystic dysplastic kidney. However, it may be difficult to differentiate segmental multicystic dysplastic kidney from cystic nephroma on the basis of imaging alone (19). Visualization of an ectopic ureterocele also suggests a diagnosis of multicystic dysplastic kidney (6). The absence of encapsulation and the presence of nearby cysts that are separate from the main conglomerate mass of cysts should allow differentiation of localized cystic disease of the kidney from MCRT (20).
Because neither the clinical nor the imaging features of MCRT can predict its histologic characteristics, surgery—either nephrectomy or nephron-sparing surgery—is required for both diagnosis and treatment (6). If pathologic analysis proves that the tumor is a CPDN, regular noninvasive monitoring is suggested because the presence of blastemal cells in the septa of a CPDN implies the potential for more aggressive behavior, despite the usually benign course of the tumor (13).
Our patient had an uneventful recovery after undergoing nephrectomy and was doing well at her last follow-up clinic appointment 5 months after surgery.
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Footnotes
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Abbreviations: CPDN = cystic partially differentiated nephroblastoma, MCRT = multilocular cystic renal tumor
See the commentary by Takahashi et al following this article.
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References
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- Sacher P, Willi UV, Niggli F, Stallmach T. Cystic nephroma: a rare benign renal tumor. Pediatr Surg Int 1998;13:197–199.[CrossRef][Medline]
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- Lowe LH, Isuani BH, Heller RM, et al. Pediatric renal masses: Wilms tumor and beyond. RadioGraphics 2000;20:1585–1603.[Abstract/Free Full Text]
- Edmunds W. Cystic adenoma of the kidney. Trans Pathol Soc Lond 1892;43:89–90.
- Agrons GA, Wagner BJ, Davidson AJ, Suarez ES. Multilocular cystic renal tumor in children: radiologic-pathologic correlation. RadioGraphics 1995;15:653–669.[Abstract]
- Parienty RA, Pradel J, Imbert MC, Picard JD, Savart P. Computed tomography of multilocular cystic nephroma. Radiology 1981;140:135–139.[Abstract/Free Full Text]
- Banner MP, Pollack HM, Chatten J, Witzleben C. Multilocular renal cysts: radiologic-pathologic correlation. AJR Am J Roentgenol 1981;136:239–247.[Abstract/Free Full Text]
- Madewell JE, Goldman SM, Davis CJ Jr, Hartman DS, Feigin DS, Lichtenstein JE. Multilocular cystic nephroma: a radiographic-pathologic correlation of 58 patients. Radiology 1983;146:309–321.[Abstract/Free Full Text]
- Sodhi KS, Suri S, Samujh R, Rao KL, Vaiphei K, Saxena AK. Bilateral multilocular cystic nephromas: a rare occurrence. Br J Radiol 2005;78: 450–452.[Abstract/Free Full Text]
- Michal M, Syrucek M. Benign mixed epithelial and stromal tumor of the kidney. Pathol Res Pract 1998;194:445–448.[Medline]
- Antic T, Perry KT, Harrison K, et al. Mixed epithelial and stromal tumor of the kidney and cystic nephroma share overlapping features: reappraisal of 15 lesions. Arch Pathol Lab Med 2006;130:80–85.[Medline]
- Joshi VV, Beckwith JB. Multilocular cyst of the kidney (cystic nephroma) and cystic, partially differentiated nephroblastoma: terminology and criteria for diagnosis. Cancer 1989;64:466–479.[CrossRef][Medline]
- Wood BP, Muurahainen N, Anderson VM, et al. Multicystic nephroblastoma: ultrasound diagnosis (with a pathologic-anatomic commentary). Pediatr Radiol 1982;12:43–47.[CrossRef][Medline]
- Geller E, Smergel EM, Lowry PA. Renal neoplasms of childhood. Radiol Clin North Am 1997; 35:1391–1413.[Medline]
- Abara OE, Liu P, Churchill BM, Mancer K. Magnetic resonance imaging of cystic, partially differentiated nephroblastoma. Urology 1990;36: 424–427.[CrossRef][Medline]
- Dikengil A, Benson M, Sanders L, Newhouse JH. MRI of multilocular cystic nephroma. Urol Radiol 1988;10:95–99.[Medline]
- Kettritz U, Semelka RC, Siegelman ES, Shoenut JP, Mitchell DG. Multilocular cystic nephroma: MR imaging appearance with current techniques, including gadolinium enhancement. J Magn Reson Imaging 1996;6:145–148.[Medline]
- Hopkins JK, Giles HW Jr, Wyatt-Ashmead J, Bigler SA. Best cases from the AFIP: cystic nephroma. RadioGraphics 2004;24:589–593.[Free Full Text]
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History
Imaging Findings
