Renal Clear Cell Sarcoma
Clear cell sarcoma of the kidney is a rare malignant mesenchymal tumor occurring in children.
Clear cell sarcoma comprises 4% of pediatric renal tumors.
It occurs usually at 2–3 years of age and it is extremely rare before 6 months.
Male-to-female ratio is 1.6:1.
The tumor usually shows the epicenter at the renal medulla.
The treatment consists of surgical resection, when possible, followed by chemotherapy and radiotherapy.
With current treatment (addition of doxorubicin to chemotherapeutic protocols), outcome has improved with a 5-year overall survival of 75–90%. Bone metastases are common, and unusual sites, such as soft tissues of orbit, may occur. Brain metastases are more common, due to blood-brain barrier which impedes effective chemotherapy. True stage I disease has a favorable prognosis, and chemotherapy protocols are stage-dependent (Argani et al. 2000).
Clear cell sarcoma presents as a well circumscribed, firm, gray mass, frequently located in the renal medulla.
Vimentin, BCL2, and cyclin D1 are typically positive, whereas CD34, S100, desmin, cytokeratin, and epithelial membrane antigen (EMA) are negative.
Roughly 10% of clear cell sarcomas harbor the chromosome translocation t(10;17) representing a YWHAE-FAM22 gene fusion, with the remaining cases having other mutation such as BCOR-CCNB3 fusion and EGFR mutations (Aw and Chang 2019).
Differential diagnosis includes other pediatric small round blue cell tumors, nephroblastoma, and other sarcomas, depending on the prominent patterns above described.
References and Further Reading
- Aw SJ, Chang KTE (2019). Clear cell sarcoma of the kidney. Archives of Pathology & Laboratory Medicine. [Epub ahead of print].Google Scholar