Epithelioid sarcoma

Clinical features

  • Accounts for less than 10% of non-rhabdomyosarcomas in children
  • Adolescents and young adults
  • Male predisposition
  • Painless dermal or subcutaneous nodules
  • Extremities (hands, fingers, wrist and legs or genital)
  • Superficial lesions

 

Fig 37 – Epithelioid Sarcoma – Aggregates and dispersed cells (Giemsa)
Fig 38 - Epithelioid Sarcoma – Large epithelioid cell groups (Giemsa)
Fig 39a - Epithelioid Sarcoma – Large epithelioid cells: cells are polygonal with dense cytoplasm (Giemsa)
Fig 39b - Epithelioid Sarcoma – Immunostaining with EMA
Fig 39c - Epithelioid Sarcoma – Immunostaining with vimentin

 

 

  • Bloody aspirates
  • Poor cellular smears
  • Necrotic background
  • Dispersed cell pattern or nests
  • Cells with well-defined cell borders, with intercellular spaces
  • Large polygonal epithelioid cells , spindle rhabdoid or multinucleated
    • Irregular nuclei contour  (round, oval, elongated or pleomorphic)
    • Prominent nucleoli
    • Dense cytoplasm with well-defined borders
    • Rhabdoid inclusions

 

Immunocytochemistry

  • Cytokeratins: Positive
  • EMA: Positive
  • CD34: Positive (50%)
  • Vimentin: Positive (perinuclear)
  • Desmin : positive
  • VE-cadherin: Positive
  • INI 1: Positive
  • E-cadherin: Negative
  • CD31: Negative (generally, rare positive cases are reported)

 

Electron microscopy:

  • Microvilli
  • Typical irregular nuclei contour and prominent nucleoli
  • Cytoplasm with:
    • Intermediate filaments
    • Abundant polyribosome, rough endoplasmic reticulum
    • Occasional lipid droplets and degenerative vacuoles surrounded by filopodia or microvilli
  • Desmosome-like junctions
  • Small intercellular spaces

 

Genetic studies:

  • DNA copy number changes, gains>losses, including +11q13, 1q21-q23, 6p21.3, 9q31-qter, losses at 9pter-p23, 13q22-q32 (4)           

 

Differential Diagnosis

  • Metastatic carcinoma (squamous)
    • Cells with are in syncytial clusters without the typical well-defined cell borders, and intercellular spaces of epithelioid sarcoma
  • Melanoma
    • S-100 protein: Positive
    • HMB45: Positive
  • Synovial sarcoma
    • Distinction can be difficult
    • CD34:Negative
    • t(X:18)
  • Hemangioendothelioma
    • Cd31 : Positive

 

Main points

  • Local recurrences
  • Metastasis in 45% of the cases (lymph nodes ,lungs, skin )
  • Poor prognostic features:
    • Axial tumour
    • Deep tumour
    • Large size
    • Haemorrhage
    • Necrosis
    • Mitosis
    • Rhabdoid features
    • Angiolymphatic invasion
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