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Kidney tumor - cysts, children, adult benign

Benign (usually) adult tumors

Cystic nephroma


Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 26 January 2012, last major update January 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Unilateral, solitary and multiloculated benign tumor with small non-communicating cysts containing clear colorless fluid; cysts have flat to hobnail epithelial lining
● Also called multilocular renal cyst
● Part of a spectrum of tumors that fall under the heading renal epithelial and stromal tumor which includes mixed epithelial and stromal tumor (Am J Surg Pathol 2009;33:72, Am J Surg Pathol 2007;31:489, Arch Pathol Lab Med 2006;130:80)

Epidemiology
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● Children less than 5 years old (usually boys) and adults ages 40-69 years (80%+ women)

Clinical features
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● Patients usually asymptomatic, may have abdominal mass or obstructive symptoms

Case reports
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● 16 month old boy (Radiographics 2004;24:589)
● 72 year old woman (Arch Pathol Lab Med 2001;125:828)

Treatment
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● Partial nephrectomy

Gross description
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● Large (5-10 cm), unilateral and solitary multiloculated tumor composed of multiple non-communicating thin-walled cysts of varying size that are filled with clear fluid
● Sharply demarcated from adjacent kidney by thick fibrous capsule; surface is nodular

Gross images
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Multiple thin walled cysts


Tumor has multiple cystic structures which do not communicate with each other or the renal pelvis


Tumor of upper pole

Micro description
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● Cysts lined by flat / cuboidal / hobnail cells separated by fibrous cysts that may have an ovarian stroma-like appearance
● No renal parenchyma (present in polycystic disease) or blastema / embryonal elements (present in cystic partially differentiated nephroblastoma) or nests of clear cells (seen in clear cell carcinoma) are present within the cyst septae
● The stroma may contain smooth muscle, skeletal muscle, cartilage or microscopic cysts lined by bland cuboidal cells that appear to be abortive tubules

Micro images
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Small and large cysts separated by thin fibrous septa

   
Cysts are lined by flattened epithelium


Cuboidal epithelial cells line the cyst


Only mature elements are present in the septa


Cysts are separated by septa of a distinctive type of fibrous connective tissue with no renal nephron elements in septa


Epithelial cells lining the cysts vary from flattened to low cuboidal or even columnar


Occasional lining epithelial cells exhibit nuclear enlargement and hyperchromasia


Case report - 72 year old woman: Figure 1: MRI, T1 shows complex cystic mass of right kidney; fig 2: 14 cm, white-tan, bosselated tumor; fig 3: septa and solid areas have mature fibrous tissue; fig 4A: keratin+ cyst epithelium; 4B: vimentin+ stroma

   

CK19+


Smooth muscle actin, ER, CD10 and high molecular weight keratin

Cytology description
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● Sparse epithelial cells with moderate nuclear atypia (Acta Cytol 2008;52:91)

Positive stains
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● Keratin in epithelium
● Vimentin and desmin in stromal cells, ER / PR in ovarian-type stroma

Electron microscopy description
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● Long cilia and other features of collecting tubules in cyst lining

Differential diagnosis
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Pediatric:
Wilms’ tumor: must sample extensively to exclude blastema; has expansile solid regions of nephroblastomatous tissue not confined by cystic spaces
Cystic partially differentiated nephroblastoma: nephroblastomatous tissue confined to cyst wall; no expansile solid regions

Adult:
Cystic renal cell carcinoma: nests of malignant clear cells in septa
Lymphangioma: D2-40+ endothelial lining of cyst wall

Additional references
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eMedicine

End of Kidney tumor - cysts, children, adult benign > Benign (usually) adult tumors > Cystic nephroma


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