| Discussion: |
Discussion: Multilocular cystic nephromas are idiopathic, benign, and rare renal neoplasms. Other names that cystic nephromas go by are cystic nephroblastoma and benign multilocular cystic nephromas. Cystic nephroblastoma is a confusing term, considering that nephroblastoma is synonymous with a Wilm’s tumor. Several studies have concluded that there is a biphasic age and sex distribution: Two-thirds of these tumors occur in the male pediatric population ranging between the ages of 3 months to two years of age; the other third occur primarily with females in their 50-60’s. The symptoms also vary with the age distribution. Children typically present with an enlarging and palpable flank or abdominal mass. Adults present with nonspecific symptoms such as UTI, flank pain, and HTN. Hematuria is a symptom that can be present with either of the two age groups.
The pathologic appearance of cystic nephromas are well-circumscribed masses that have a thick fibrous capsule. These capsules contain multiple fluid-filled, non-communicating cystic spaces that are separated by connective tissue septa. The mass is most commonly unilateral, solitary, and often in the lower pole of the kidney. Microscopically the locules are lined with flattened cuboidal or slightly protruding epithelial cells. The fibrous septa may contain well-differentiated renal tubules. No reports or studies have documented any cases of malignant transformation.
Imaging: CT and US are the two most commonly used imaging techniques used to identify the cystic nephroma. On US, the origin of the nephroma shows a diagnostic claw or “beak” of normal-appearing parenchyma at the periphery of the mass. This displaces the collecting system. US seems to be better than CT at distinguishing the internal architecture of the nephroma since the connective tissue septa have the same attenuation as the cystic contents of the mass on CT.
Treatment: Treatment is simply surgical excision of the nephroma, whether it entails a total nephrectomy or a nephron-sparing surgery with tumor-free margins. This treatment is curative.
Differential Diagnosis: Cystic Partially Differentiated Nephroblastoma (CPDN), Wilms tumor, polycystic kidney disease (which, however, is much more commonly bilateral), multicystic dysplastic kidney (which can be segmental and involve only the upper or lower pole)