Soft tissue tumours with a myxoid appearance

Myxoid liposarcoma:

  • Myxoid background
  • Chicken wire like curvilinear blood vessels
  • Lipoblasts
  • Mucin pools
  • When >5% round cell component- Myxoid round cell liposarcoma,
  • t(12;16)(q13;p11) karyotype leading to fusion of DDIT3 (CHOP) with FUS (TLS).
  • S100 positive
  • younger patients

Low grade fibromyxoid sarcoma

  • on low power appearance of lobular areas of myxoid stroma seperated by collagenous septae, myxoid areas may have a more whorled appearance
  • Vessels more distended
  • vague appearance of collagen within myxoid area between cells
  • Areas of higher cellularity
  • Difficult to find mitoses
  • MUC4 gene unregulation
  • any age also younger patients
  • sometimes giant collagen rosettes

Myxoid fibrosarcoma

  • Pleomorphic
  • Myxoid
  • atypical mitotic figures
  • areas of high cellularity
  • pseudolipoblasts
  • mostly in elderly, in limb girdles, abdominal and retroperitoneal extremely rare

Other rarer cases in the malignant myxoid spindle cell DD include Extraskeletal myxoid chondrosarcoma, acral myxoinflammatory fibroblastic sarcoma

Extraskeletal myxoid chondrosarcoma

  • deep soft tissue of proximal extremities
  • multilobulated with myxoid matrix with small uniform round cells with minimal atypia finely granular eosinophilic cytoplasm arranged in clusters, cords and delicate networks within a prominent myxoid matrix
  • EWRS – NR4A3 fusion

Nodular fasciitis

  • Benign
  • Encapsulated
  • slit like spaces
  • extravasated rbcs
  • assoc with infection, trauma

DD of those with pleomorphic and myxoid appearance:

  • Myxoid fibrosarcoma
  • Pleomorphic liposarcoma


WHO Soft tissue tumor classification.2002

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