Extraskeletal myxoid chondrosarcoma

Clinical features

  • Rare in children
  • Can be congenital
  • Lower extremities, buttocks, head and neck
  • Deep seated and painless
  • Considered as an indolent, low-grade soft tissue sarcoma with a tendency toward recurrence

 

Fig 26 - Extraskeletal myxoid chondrosarcoma - Single cells or cells in small isolated groups or matrix embedded aggregates. Long delicate spicules of this matrix, with sharply defined edges, blend with the myxoid background (H&E).
Fig 27 - Extraskeletal myxoid chondrosarcoma - Single neoplastic cells with oval to round nucleus and homogeneous acidophilic cytoplasm (H&E)-corner- Neoplastic cells can be multinucleated, with single prominent nucleoli (H&E)
Fig 28 - Extraskeletal myxoid chondrosarcoma – Remark the round nucleus with the abundant cytoplasm (Giemsa)

 

  • Aspirate with abundant whitish fluid
  • Metachromatic myxoid  background
  • Poor to rich smears
  • Bimodal cell pattern: round to oval cells and spindle cells
  • Single cells , cords or clusters
  • Nuclei with fine granular chromatin
  • Nuclear grooves can be present
  • Small prominent nucleoli
  •  Delicate and scant to moderate amounts of pale blue cytoplasm.
  • Myxoid/chondroid matrix (almost always present) embedding cell aggregates
  • Fibrillary to dense stroma with sharp borders although some fragments of matrix have long delicate spicules that blend with the background
  • Multinucleated cells

 

Histochemical Stains

  • sulphated glycosaminoglycan’s stain, without staining to hyaluronic acid
  • Alcian Blue PH 1

Immunocytochemistry

  • S100 Protein: Positive
  • Vimentin: Positive
  • Lysozyme: Positive
  • Bcl-2: positive
  • CD99: positive
  • CD57: positive
  • EMA and cytokeratin’s (AE1AE3, CAM5.2, CEA): Negative
  • Neuroendocrine markers: Positive

Electron microscopy

  • Rudimentary cell junctions
  • Cytoplasm with: well developed endoplasmic reticulum, Golgi and many mitochondria.
  • RER distended and filled with parallel microtubules of 24-nm
  • Cytoplasmic Glycogen

Genetic studies

  • t (9; 22) (q22-31; 11-12) - EWS/TEC gene fusion-(75%)
  • t(9;17)- described in some variants

Differential Diagnosis

  • Rhabdomyosarcoma
    • Muscle differentiation (immunohistochemical and electron microscopy)
  • Myxoid liposarcoma
    • Lipoblasts with scalloped nuclei clustered around branching capillaries
    • Chicken wire
  • Chordoma
    • Also has metachromatic myxoid stroma
    • Also has tumour cells single or arranged in cords
    • Presence of physaliphorous cells
    • Epithelial markers : Positive
  • Extra renal rhabdoid tumour
    • Rarely a myxoid lesion
    • Prominent eosinophilic nucleoli
    • Eosinophilic para nuclear cytoplasmic inclusions.
    • Cytokeratin’s: Positive

Main points

  • Lung metastasis are frequent at presentation, in high grade tumours
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