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Kidney tumor - cysts, children, adult benign

Childhood neoplasms

Clear cell sarcoma

Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 30 December 2012, last major update December 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.


● Rare tumor composed of uniform, small round cells with clear cytoplasm and evenly distributed fine chromatin separated by a vascular network (eMedicine)


● Rare (20 cases per year); 3% of all pediatric renal tumors
● Mean age of diagnosis: 36 months (range, 2 months-14 years)
● Rarely diagnosed in adolescents / adults (Am J Surg Pathol 1999;23:1455)
● 2/3 male


Clinical features

● Frequent recurrence / relapse with metastases to bone (Hum Pathol 1985;16:1219)
● Other sites of metastases include lymph nodes (29% at presentation), CNS, lung, liver and muscle
● Overall, survival varies with stage (5 year survival is 97% for stage I vs. 50% for stage IV, Am J Surg Pathol 2000;24:4)
● Highly responsive to treatment with doxorubicin / vincristine / actinomycin
● Death is more common after combination therapy utilizing other agents

Case reports

● Congenital tumor with metastases (Virchows Arch 2005;446:566)
● 19 year old man with renal mass (University of Pittsburgh case #201)

Gross description

● Unilateral and unicentric mass with irregular but sharp tumor-kidney interface
● Large (mean: 11 cm); centered in central kidney or medulla
● Cut surface is homogenous tan / gray or gelatinous and firm with occasional cysts

Gross images

Large tan to tan-yellow tumor

Micro description

● Classic pattern: nests or cords of small, polygonal cells with indistinct cell margins, light staining cytoplasm and round nuclei with fine chromatin and grooves (similar to papillary thyroid carcinoma)
● No nucleoli, rare mitoses; 20% have clear cells (due to vacuoles)
● Cords are created by an arborizing network of vascular septae
● Although the border appears sharp at low power, high power reveals infiltration of the cells around the normal tubules / glomeruli at the periphery
● Vascular invasion common
● The classic pattern is almost always focally present, but other patterns include myxoid, sclerosing (includes hyalinizing which has osteoid-like pattern resembling osteosarcoma), cellular, epithelioid, palisading, spindle / storiform and anaplastic
● Recurrences / metastases may have a deceptively bland histologic appearance

Micro images

Tumor-kidney junction showing entrapment of individual nephrons by tumor cells extending into the adjacent renal parenchyma

Sheets of monotonous cells with indistinct cell margins, pale cytoplasm and round / oval nuclei with fine chromatin

Various images

Cell cords

Numerous cytoplasmic vesicles

In this field, the tumor cytoplasm is more compact and less vesicular, and the nuclei are pale and frequently empty

Cord cells are spindled, but vascular septa are still recognizable

Proliferation of septal cells imparts a prominent spindled pattern


Pleomorphic tumor giant cells

Hyalinizing pattern

Epithelioid pattern

Filigree pattern

Myxoid and cystic pattern

Palisading pattern reminiscent of schwannoma

Pericytomatous pattern

Sclerosing pattern


Comparison with nephroblastoma:

Nephroblastoma (left) and clear cell sarcoma (right)-note the more uniform appearance and paler blue color of clear cell sarcoma

Entrapped single renal tubules with cystic dilatation of one tubule, resembles nephroblastoma

Cord cells have become condensed, creating cohesive epithelioid ribbons that can be confused with nephroblastoma

Cytology description

● Cells with moderate pale blue cytoplasm (Cytopathology 2008;19:80), cord cells with few stromal fragments
● Spindle cell variant has myxoid stromal fragments and septal cells
● Anaplastic variant has bizarre pleomorphic nuclei, coarse chromatin and atypical mitotic figures (Diagn Cytopathol 2005;33:83)

Cytology images

Irregular nuclear borders, coarse chromatin and nuclear folding / grooves

Positive stains

● Vimentin

Negative stains

● Keratin, EMA, S100, CD99, WT1, p53, desmin, CEA, synaptophysin and CD34

Molecular description

● t(10;17)(q22;p13), t(10;17)(q11;p12) and interstitial deletions of #14q (Arch Pathol Lab Med 2007;131:446)

Molecular images

t(10;17)(q22;p13) and interstitial deletion of 14q

E.M. description

● High N:C ratio
● Cytoplasm composed of complex processes surrounding abundant intercellular matrix with rare organelles, sparse cytoplasmic filaments and primitive cell junctions

Differential diagnosis

Wilms’ tumor: pushing border, more aggressively invasive, cells are less uniform and more hyperchromatic and epithelioid areas are keratin+

End of Kidney tumor - cysts, children, adult benign > Childhood neoplasms > Clear cell sarcoma

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