Multilocular Cystic Renal Tumor in Children

Radiologic-Pathologic Correlation

Abstract Introduction and Historical Background Clinical Features

Pathologic Features Radiologic Features Differential Diagnosis Treatment and Prognosis

Summary Source Information References

Radiologic Features

Cystic nephroma and CPDN cannot be distinguished radiographically, just as they cannot be distinguished by gross anatomic appearance. In either variety of multilocular cystic renal tumor, radiography reveals displacement of bowel and adjacent structures by a soft-tissue flank mass if the lesion is of sufficient size. Small curvilinear calcifications are occasionally identified (Figure 6) (16). Rarely, a mass is not suspected clinically, in which case excretory urography fortuitously reveals nonspecific stretching, displacement, and attenuation of the renal collecting system by the mass and possibly demonstrates herniated tumor cysts within the renal pelvis (Figure 7).

The sonographic appearance of multilocular cystic renal tumor includes multiple anechoic spaces traversed by thin septa and no solid elements (16,24,26,27,28,29). However, tumors with smaller loculi present innumerable acoustic interfaces to the ultrasound beam, mimicking echogenic solid masses (26,29). The renal origin of the mass can be confirmed in most cases by recognizing a beak or "claw" of normal renal parenchyma around the periphery of a well-defined mass (Figure 1a), splaying or displacement of the renal collecting system, and synchronous motion of the mass and kidney with respiratory excursion.

Typical CT findings include a sharply circumscribed, multiseptated renal mass with the attenuation value of the cyst contents approximating or slightly exceeding that of water (16,30). However, the entire mass or portions of the mass may appear solid (Figure 8) if smaller cysts result in closer approximation of the soft-tissue septa (16). The septations enhance following contrast material administration, but contrast material does not accumulate within individual loculi.

Magnetic resonance (MR) imaging findings have been reported in one case of CPDN and two cases of cystic nephroma (31,32). Both examples of cystic nephroma demonstrated low signal intensity of the tumor capsule on all MR images, regardless of pulse sequence used. Variable signal intensity from the cyst contents was attributed to differing concentrations of old hemorrhage and protein, but this explanation was not conclusively established. The AFIP archives currently contain two cases of cystic nephroma studied with MR imaging. In both cases, low signal intensity was seen in the tumor capsule and septa on T1-weighted images (Figure 9). In one case, T2-weighted and gadolinium-enhanced T1-weighted images were also obtained (Figure 10). The cyst septa enhanced following administration of gadolinium. The fluid contents of the cyst loculi displayed high signal intensity on T2-weighted images and were slightly less bright than the gallbladder.

Two patients in the prior AFIP series (16) underwent scintigraphy of the kidneys. In both patients, scintigrams demonstrated a defect corresponding to the renal mass. Our series includes four patients who underwent scintigraphy, with technetium-99m diethylenetriaminepentaacetic acid (DTPA) in three and Tc-99m dimercaptosuccinate (DMSA) in one. In each case, a large defect in radiotracer accumulation was evident in the renal fossa. In one case, septa were suggested by faint activity within the mass (Figure 11).

Abstract Introduction and Historical Background Clinical Features

Pathologic Features Radiologic Features Differential Diagnosis Treatment and Prognosis

Summary Source Information References