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Clear cell sarcoma

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Clinical features

  • Malignant mesenchymal neoplasm
  • Rare renal tumour (3-5% of all paediatric kidney tumours)
  • It occurs almost exclusively between the ages of 6 months and two years
  • Male predominance
  • Not associated with malformations or syndromes
  • Propensity for bone (skull) and visceral metastasis
  • Single-centre tumour
  • High-risk tumour (SIOP-2001 revised working classification of renal tumours of childhood)


Fig 9a – Clear cell sarcoma of the kidney- Cords of polygonal cells. Remark the chicken wire vasculature (H&E)

  • Variable cellularity
  • Background with metachromatic mucoid-like material rich in glycoproteins, seen in Giemsa-stained slides
  • Large cells that are dispersed or in perivascular pattern
  • Round, oval or short spindle bland nuclei with vesicular chromatin
  • Nuclear grooves sometimes present
  • Inconspicuous nucleoli
  • Fragile and pale cytoplasm
  • Myxoid stroma may be present
  • Necrosis
  • The presence of confounding renal tubules entrapped by the tumour that can appear in the smears, can lead to erroneous diagnosis of Wilms´ tumour (these tubules are CD56(NCAM) negative and EMA positive


  • Vimentin: positive, but moderate not strong- “ ….a strong positive Vimentin  points away CCSK”
  • CD56 (NCAM)-positive (diffuse)
  • CD99: negative
  • CD117 :positive
  • Bcl2: positive
  • EMA: negative
  • Desmin: negative
  • CD10:negative (rare cases reported as positive)
  • CD15:negative
  • WT1: negative

Differential diagnosis

  • Nephroblastoma (blastemal type)
    • Regular nuclei with fine chromatin
    • Cytoplasm is very scarce (cells in CCS bare more cytoplasm)
    • Sometimes epithelial markers can show poorly differentiated or isolated cells with epithelial differentiation
    • WT1: Positive
  • Mesoblastic nephroma
    • Generally diagnosed within the first six months of life
    • Bland, small spindle cells
    •  CD56 (NCAM): negative
    • WT1: positive (cytoplasm)
  • Neuroblastoma
    • Nuclei with salt-and-pepper chromatin
    • Neuroblasts at different stages of maturation
    • Fibrillary matrix
    • Vimentin: usually negative
    • Synaptophysin: positive
    • NSE: positive
  • PNET
    • Most common in young adults
    • Nuclei with coarse chromatin
    • CD99: positive
    • t (11:22) (q24; q12)
  • Rhabdoid tumour
    • Cells with a rhabdoid-like pattern:
      • Prominent eosinophilic nucleoli
      • Eosinophilic para nuclear cytoplasmic inclusions
      • Cytokeratin’s: positive
      • CD56(NCAM): negative
      • INI 1: negative

Main points

  • Undifferentiated sarcoma, nearly exclusively in the kidneys
  • No familial specific malformations, syndromes or genetic abnormalities associated
  • Poor prognostic changes: necrosis
  • Even low-stage tumours have poor prognosis
  • Also known as bone-metastasizing renal cell tumour
  • Metastasis can occur 3 to 10 years after diagnosis
  • Recurring genetic defects have been reported:  t(10;17), del(14)(q24.1q31.1)