Go back to clinical information and images

Diagnosis: Clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) is a rare malignant renal tumour of childhood, characterized histologically by variably clear tumour cells and distinctive arborizing fibrovascular septa, and molecularly by BCOR mutations or YWHAE::NUTM2 gene fusion. CCSK constitutes 3–5% of malignant renal tumours in childhood, ranking a distant second after nephroblastoma. The M:F ratio is 2:1. The mean age at diagnosis is 3 years. CCSK has varied histological patterns. The classic pattern is most common and is usually present at least focally. The features include plump ovoid tumour cells demarcated into broad trabeculae or nests by distinctive arborizing fibrovascular septa. Tumour cells have barely perceptible cytoplasm and monomorphic nuclei with dispersed chromatin and indistinct nucleoli. The nuclei and cytoplasm often have a clear appearance, from which this tumour derives its name. The cellular pattern has similar tumour cells that are more closely packed, with frequent nuclear overlapping. The myxoid pattern features increased mucopolysaccharide matrix, which may form mucoid pools and cysts. The sclerosing pattern features hyalinized collagen, which may resemble osteoid. The epithelioid pattern has tumour cells aligned in acini or elongated trabeculae mimicking the epithelial structures that may be seen in nephroblastoma. The palisading pattern features nuclear palisading that resembles Verocay bodies of schwannomas. The spindled pattern has elongated tumour cells resembling those of spindle cell sarcomas. Rare tumours have anaplasia, defined in the same way as for nephroblastomas. Posttreatment relapses may resemble myxoma or fibromatosis histologically.

Immunohistochemistry for both cyclin D1 and BCOR in a diffuse nuclear staining pattern provides robust support for the diagnosis of CCSK. However, although sensitive, cyclin D1 is not perfectly specific; and BCOR is neither perfectly sensitive nor specific. Other positive markers include vimentin, p75-NGFR, BCL2, TLE1, and SATB2. CCSK is negative for CD34, S100, desmin, cytokeratins, WT1, and EMA.

Prognosis: CCSK has 5-year event-free and overall survival rates of 65–85% and 75–90%, respectively, with intensive multiagent chemotherapy and radiation therapy. Approximately 16% of patients relapse. Relapse may be late. CCSK may metastasize to unusual sites such as bone, orbit, and brain. The clinical course is not predicted by histological pattern or mutation findings.

(The above text was taken from: WHO Classification of Tumours. Paediatric tumours [Internet]. Lyon (France): IARC. 5th ed. 2022; vol. 7. Available from: https://tumourclassification.iarc.who.int/chapters/44).

See the chapter: Renal Neoplasms of our Tutorial (only Spanish version).

Go back to clinical information and images

References

[Top]

Go back to clinical information and images