Excerpt from Multilocular Cystic Nephroma

Synonyms, Key Words, and Related Terms: multilocular cystic renal tumor, cystic nephroma, cystic partially differentiated nephroblastoma, CPDN, multilocular cystic renal tumor, benign multilocular cystic nephroma, polycystic nephroblastoma, differentiated nephroblastoma, well-differentiated polycystic Wilms tumor, benign cystic differentiated nephroblastoma, cystic partially differentiated nephroblastoma

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Background: In the past, multilocular cystic renal tumors have been considered to be lesions of developmental origin, hamartomas, or hamartomas with malignant potential. In 1956, Boggs and Kimmelstiel first proposed the true neoplastic nature of the lesions in a case report, suggesting the term benign multilocular cystic nephroma for this condition.

More recently, Joshi and Beckwith proposed a modification to the existing terminology. Their modification emphasized a neoplastic rather than a developmental or hamartomatous origin. First, they recommended that the term cystic nephroma be used to describe a multicystic tumor lacking blastemal or other embryonal elements. Second, they suggested that the term cystic partially differentiated nephroblastoma (CPDN) be used to denote a predominantly cystic lesion without nodular solid regions and in which the septa contain blastemal or other embryonal elements. Furthermore, they proposed that both terms be used as subsets of the category term multilocular cystic renal tumor.

Pathophysiology: Multilocular cystic renal tumor is characterized as a solitary, well-circumscribed, multiseptated mass of noncommunicating fluid-filled loculi that is surrounded by a thick fibrous capsule and compressed renal parenchyma. The mass is typically large. Madewell et al discovered that the mean size of the mass is 7.6 X 9.7 cm. Kettritz et al reported solitary tumors sized 3.3-13 cm, with an average maximum diameter of 6.7 cm.

The most commonly reported location for this tumor originates at the lower pole, although tumors have been known to originate in other areas. Kettritz et al discovered tumors that originated in the middle third of the kidney in 5 patients, in the upper pole of the kidney in 1 patient, and in the lower pole of the kidney in 1 patient. All 7 lesions were multiseptated cysts, arising in the right kidney in 3 patients and in the left kidney in 4 patients.

The contents of the cyst consist of either clear-to-yellow fluid (similar to serum) or thick myxomatous gel. Although complications are unusual, cyst herniation into the renal pelvis has been described as occurring most frequently. On gross inspection, solid nodules of tissue are not discernible, and hemorrhage and necrosis is usually not found. Calcification is also uncommon.

Frequency:

In the US: Multilocular cystic renal tumors are rare; therefore, determining the true prevalence and the age and sex distributions is difficult.

Mortality/Morbidity: No mortality is associated with this disease. Morbidity is related to the single functional kidney.

Race: Multilocular cystic nephroma has no racial predilection.

Sex: Multilocular cystic renal tumors have been noted to affect males, predominantly in childhood, and females, predominantly in adulthood.

Age: Castillo et al found that two thirds of the tumors occurred in children aged 3 months to 2 years, with a male-to-female predominance ratio of 2:1. Of tumors in this group, almost 50% contained blastema; therefore, they were classified as CPDNs.

Of patients aged 30 years or older (approximately 30% of patients), an 8:1 female-to-male predominance was found. Of this group, fewer than 20% of tumors were CPDNs. Other groups have reported similar results. Madewell et al found that, in childhood, 73% of cases occurred in boys younger than 4 years. In patients older than 4 years, 89% of cases occurred in females, who presented with findings of an abdominal mass.

Anatomy: Anatomically, cystic nephroma and CPDN are identical; however, they are histologically distinct. In cystic nephroma, as defined by Joshi and Beckwith, the septa consist of fibrous tissue that may contain well-differentiated renal tubules but no poorly differentiated .....