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Eble JN, Sauter G., Epstein JI, Sesterhenn IA - iarc

Eble JN, Sauter G., Epstein JI, Sesterhenn IA - iarc

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Clear cell sarcoma<br />

P. Argani<br />

Definition<br />

Clear cell sarcoma of the kidney (CCSK)<br />

is a rare paediatric renal sarcoma with a<br />

propensity to metastasize to bone.<br />

ICD-O code 9044/3<br />

Clinical features<br />

CCSK comprises approximately 3% of<br />

malignant paediatric renal tumours {114}.<br />

CCSK is not associated with Wilms tumourrelated<br />

syndromes or nephrogenic rests.<br />

The male to female ratio is 2:1. The mean<br />

age at diagnosis is 36 months. The frequency<br />

of osseous metastases led to the<br />

proposed name "bone metastasizing renal<br />

tumour of childhood" {1630}.<br />

Macroscopy<br />

CCSKs are typically large (mean diameter<br />

11 cm) and centred in the renal<br />

medulla, and always unicentric. CCSK<br />

are unencapsulated but circumscribed,<br />

tan, soft, and mucoid, and almost always<br />

focally cystic.<br />

Histopathology<br />

The classic pattern of CCSK features<br />

nests or cords of cells separated by regularly<br />

spaced, arborizing fibrovascular<br />

septa {114,196,1311,1628,1629,1630,<br />

1783}. The cord cells may be epithelioid<br />

or spindled, and are loosely separated<br />

by extracellular myxoid material that<br />

mimics clear cytoplasm. Nuclei are<br />

round to oval shaped, have fine chromatin,<br />

and lack prominent nucleoli. The<br />

septa may be thin, regularly branching<br />

"chicken-wire" capillaries, or thickened<br />

sheaths of fibroblastic cells surrounding<br />

a central capillary. While CCSKs are<br />

grossly circumscribed, they characteristically<br />

have subtly infiltrative borders,<br />

entrapping isolated native nephrons.<br />

CCSK has varied histopathologic pat-<br />

A<br />

B<br />

Fig. 1.78 Clear cell sarcoma of the kidney. A Classic pattern. B Acinar pattern mimicking nephroblastoma.<br />

A<br />

B<br />

Fig. 1.79 Clear cell sarcoma of the kidney. A Trabecular pattern. B Palisading pattern mimicking schwannoma.<br />

56 Tumours of the kidney

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