Clear cell sarcomas (CCS) of the kidney are a rare mesenchymal renal tumour that accounts for ~5% of primary renal neoplasms in paediatric population 1.
CCS is the second most common primary malignant renal neoplasm after Wilms tumour, with an annual incidence of 20 cases in the United States 2,3. The mean age of diagnosis is 3 years 2, although it is very rare before the age of 6 months 3,4. Males are noticed to be affected more with an M:F = 2:1 1.
CCS usually presents with a palpable abdominal mass; with haematuria and bone pain being less common.
CCS appears as a large solid mass, usually unilateral and unifocal, replacing most of the kidney or centred in the medulla 1. The cut surface appears gelatinous due to the abundance of extracellular mucopolysaccharides. Haemorrhage and necrosis are frequent findings (70%) 2.
Histologically, nine subtypes have been described 1. Most of these, however, will show some of the classic features of the tumour microscopically, consisting of cords or nests of cells surrounded by delicate branching cellular fibrovascular septa akin to chicken wire.
Although the margins of the tumour appear well defined grossly, they demonstrate infiltration into adjacent renal parenchyma with entrapment of the tubules on high power field microscopy. The entrapped tubules may become extensively dilated, giving the apparent cysts seen on gross tumour inspection 2.
These tumours usually enhance heterogeneously and to a lesser extent than the adjacent kidney, with non-enhancing foci representing haemorrhage and necrosis 5. They often cross the midline. Calcification is uncommon 5.
CCS usually appears low to intermediate on T1 weighted images and high signal on T2WI with cystic areas.
Treatment and prognosis
CCS has a worse prognosis compared to Wilms tumours, especially in those younger than 12 months of age 3. The mainstay treatment is radical nephrectomy with lymph node dissection. Relapse rate is high (20-40% of patients) 4.
The imaging appearances for CCS are non-specific and can be very similar to other primary renal neoplasms, especially Wilms tumour which is much more common. Finding of bone metastasis could suggest CCS rather than Wilms tumour 1.
- 1. Chung EM, Graeber AR, Conran RM. Renal Tumors of Childhood: Radiologic-Pathologic Correlation Part 1. The 1st Decade: From the Radiologic Pathology Archives. Radiographics. 2016;36 (2): 499-522. doi:10.1148/rg.2016150230 - Pubmed citation
- 2. Argani P, Perlman EJ, Breslow NE et-al. Clear cell sarcoma of the kidney: a review of 351 cases from the National Wilms Tumor Study Group Pathology Center. Am. J. Surg. Pathol. 2000;24 (1): 4-18. Pubmed citation
- 3. Furtwängler R, Gooskens SL, van Tinteren H et-al. Clear cell sarcomas of the kidney registered on International Society of Pediatric Oncology (SIOP) 93-01 and SIOP 2001 protocols: a report of the SIOP Renal Tumour Study Group. Eur. J. Cancer. 2013;49 (16): 3497-506. doi:10.1016/j.ejca.2013.06.036 - Pubmed citation
- 4. Gooskens SL, Furtwängler R, Vujanic GM et-al. Clear cell sarcoma of the kidney: a review. Eur. J. Cancer. 2012;48 (14): 2219-26. doi:10.1016/j.ejca.2012.04.009 - Pubmed citation
- 5. Glass RB, Davidson AJ, Fernbach SK. Clear cell sarcoma of the kidney: CT, sonographic, and pathologic correlation. Radiology. 1991;180 (3): 715-7. doi:10.1148/radiology.180.3.1871282 - Pubmed citation