4.11 Multilocular Cystic Renal Tumor

•The majority of cases occurs in patients 50–60 years of age and is seen predominantly in females by a 2:1 ratio.

•MA is a rare neoplasm that often presents as an asymptomatic renal mass.

•The clinical presentation include:

–Abdominal pain

–Abdominal mass

–Hematuria

–Dysuria

–Fever

–Hypertension

–Hypercalcemia

–Polycythemia

•Among renal tumors, MA has the highest incidence (12 %) of polycythemia.

•Several tumors can resemble MA including Wilms tumor, metastatic lung carcinoma, and metastatic papillary thyroid carcinoma; however, it is most difficult to distinguish MA from papillary renal cell carcinoma.

4.10.5 Treatment

•Metanephric adenomas are benign tumors and because of this some advocate no treatment is needed.

•Although MA is usually benign, there are a few reported cases of metastatic disease.

•Surgical resection is important in order to confirm the diagnosis and rule out papillary renal cell carcinoma.

•Surgery is curative and no other treatment is recommended.

4.11Multilocular Cystic Renal Tumor

•In 1956, Boggs and Kimmelstiel first proposed the true neoplastic nature of these lesions, suggesting the term benign multilocular cystic nephroma.

•Joshi and Beckwith proposed a modification to the existing terminology.

–Their modification emphasized a neoplastic rather than a developmental or hamartomatous origin.

–They recommended that the term cystic nephroma be used to describe a multicystic tumor lacking blastemal or other embryonal elements.

–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.

•Multilocular cystic renal tumor has a bimodal age and sex distribution and tends to occur in children (mostly boys) between 3 months and 4 years of age and in adults (mostly women) between 40 and 60 years of age.

•Multilocular cystic renal tumor are usually solitary, but bilateral tumors have been described.

•Multilocular cystic renal tumor most frequently manifests in children as a painless abdominal mass or less commonly as hematuria and urinary tract infection.

•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.

•Multilocular cystic renal tumor is a term that encompasses two histologically distinct but grossly indistinguishable renal tumors:

–Cystic nephroma

–Cystic partially differentiated nephroblastoma (CPDN)

•A cystic nephroma is a rare benign renal tumor that is also known as:

–Multilocular cystic nephroma

–Mixed epithelial stromal tumor (MEST)

–Renal epithelial stromal tumor (REST)

•Cystic nephroma is a purely multiloculated cystic mass characterized by multiple septations composed entirely of differentiated tissues, without blastemal elements.

•CPDN is also a multiloculated cystic mass without nodular solid components, but its septa contain embryonal cells.

•Multilocular cystic renal tumors primarily affect boys during early childhood, with a substantial number of the lesions containing blastema (CPDN), and adult women, with lesions that more commonly lack septal blastema (cystic nephroma).

•As a rule, nephrectomy is curative and the clinical course is benign, but CPDN may recur locally.

•Cystic nephroma and CPDN cannot be distinguished radiologically.

•The differential diagnosis includes other pediatric cystic renal tumors:

–Wilms tumor with cyst formation due to hemorrhage and necrosis

–Cystic clear cell sarcoma

–Cystic mesoblastic nephroma

–Cystic renal cell carcinoma

–Multicystic dysplastic kidney

–Segmental multicystic dysplasia in a duplicated renal collecting system

•A cystic nephroma:

–This is a benign cystic lesion of the kidney of unknown etiology.

–The first cystic nephroma was described by Edmunds in 1892 but it was called “cystic adenoma of the kidney.”

–Subsequently, it was called “multilocular cyst of the kidney”.

–Cystic nephromas usually occur before age 2 and after age 40.

–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.

–They are not commonly found in adolescents and young adults.

–In children, cystic nephromas are more commonly found in boys and in adults, it is more commonly found in females.

–Bilateral cases are exceedingly rare.

–The most common presenting symptoms and signs are:

•Flank mass

•Flank or abdominal pain

•Urinary tract infection

•Hematuria

–The histopathologic characteristics of cystic nephromas are striking.

•The gross specimen shows a cluster of noncommunicating cysts of varying sizes.

•The cysts size ranges from several millimeters to 4 cm in diameter.

•The cysts are well circumscribed by a thick outer pseudocapsule that compresses the adjacent normal renal parenchyma.

•The lesion is usually 5–10 cm in diameter and may extend beyond the normal reniform configuration into the renal pelvis and the perinephric spaces.

•The cysts are lined with flattened, cuboidal, or hobnail-appearing cells and to contain straw-yellow, proteinaceous, colloid-like fluid.

•The intervening septations conform to the cyst contours and do not form nodular masses.

–In a review of the literature, Joshi and Beckwith outlined the revised criteria for the diagnosis of cystic nephroma:

•The lesion is composed entirely of cysts and their septa.

•The lesion forms a discrete mass, well demarcated from the noncystic renal parenchyma.

•The septa are the only solid portions of the tumor, conforming to the outlines without solid expansile nodules.

•The cysts are lined by flattened, cuboidal, or hobnail-appearing epithelium.

•The septa are composed of fibrous tissue in which well-differentiated tubules may be present but poorly differentiated tissues and blastemic cells are absent.

–It is generally believed that welldifferentiated, mature renal tubules and mature heterologous tissues, such as skeletal muscle and cartilage, may be found in cystic nephromas but that hemorrhage and necrosis are not observed.

–There is controversy as to whether calcification may be found in cystic nephromas.

–Radiologically, abdominal ultrasound, MRI and CT-scan are useful but a definitive diagnosis and exclusion of an associated malignancy cannot be ensured. This is even in spite of the addition of percutaneous biopsies.

–The presence of solid components should discourage a diagnosis of cystic nephroma.

–The treatment of choice for cystic nephroma is surgical extirpation.

–Nephron-sparing surgery should be considered also.

–Cystic nephromas are benign, and the possibility of a recurrence developing after complete surgical extirpation of the neoplasm is unlikely.

•Multilocular cystic renal tumor encompasses a spectrum ranging from a purely cystic lesion lined by epithelium and fibrous septa with mature tubules (cystic nephroma) to a lesion in which the septa contain foci of blastemal cells (cystic partially differentiated nephroblastoma).

•Cystic partially differentiated nephroblastoma is distinguished from cystic Wilms tumor by the absence of expansile solid masses of nephroblastomatous tissue.

•Cystic nephroma and cystic partially differentiated nephroblastoma are uncommon, benign lesions that cannot be differentiated by means of their gross or radiographic appearance.

•Multilocular cystic renal tumors tend to manifest at two age peaks:

–In children aged 3 months to 4 years (predominantly boys with cystic partially differentiated nephroblastoma)

–In adults (pre-dominantly women with cystic nephroma)

•Patients frequently present with a painless abdominal mass, and systemic symptoms are rare. Rarely, they present with hematuria or urinary tract infection.

•Abdominal ultrasound and CT-scan findings in those with multilocular cystic renal tumor (MCRT) include:

–Large multilocular renal cystic mass sometimes extending into the renal hilum.

–A well-circumscribed, encapsulated multicystic mass with variably enhancing septa and no excretion of contrast agent into the loculi.

–The septae are of uniform thickness and only minimally hyperemic on color Doppler ultrasound.

–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.

–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.

•Cystic nephroma and CPDN are indistinguishable from one another based on their gross and radiographic appearances.

•Gross features:

–MCRT is a well-circumscribed mass with a thick fibrous capsule that contains multiple, fluid-filled, noncommunicating loculi separated by thin translucent septa.

–The loculi can range in size from microscopic to 4 cm in diameter.

•Microscopic features:

–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.

–Mature renal tubules may be seen within the septa.

–Unlike CPDN, cystic nephroma does not contain blastemal cells within the septa.

•Imaging studies demonstrate a wellcircumscribed, encapsulated mass consisting of multiple cysts from several millimeters to 4 cm in diameter, with variably enhancing septa and no excretion of contrast material into the loculi.