Desmoplastic small cell tumour

Clinical features

  • Children and young adult
  • Usually in males
  • Abdominal pain
  • Abdominal location with predilection for pelvic region, as solitary or multiple nodules
  •  ascites is a constant feature
  • Cases have been described in lungs, pleura, ovaries, pancreas, testes, cranial fossa, parotid, and soft tissues
  • Lymph node metastases are rare

 

Fig 54 - Desmoplastic small cell tumor –Single and three dimensional groups of monomorphic small round cells (H&E)
Fig 55 - Desmoplastic small cell tumor – Dense stromal fragments are mixed with neoplastic cells (H&E)
Fig 56 - Desmoplastic small cell tumor –Monotonous neoplastic cell population, nuclei with fine granular chromatin and inconspicuous nucleoli (H&E)
Fig 57 - Desmoplastic small cell tumor –Nuclear moulding (Giemsa)

 

  • Single and clusters (sheets or three-dimensional groups) of monomorphic small round cells
  • Neoplastic cells with uniform nuclei
  • Nuclear moulding
  • Fine granular chromatin
  • Inconspicuous nucleoli
  • Sparse cytoplasm
  • Stromal fragments
  • Other patterns: rhabdoid, signet ring or rosettes

 

Immunocytochemistry

  • Coexpression of desmin (dot), EMA, AE1AE3, CAM5.2 or Vimentin
  • NSE: positive
  • Myo-D1: negative
  • Smooth muscle actin: negative
  • WT1: positive
  • CD99: membranous staining negative (35% positive reported by Gerald and et al, but only cytoplasmic)
  • Chromogranin: negative

 

Genetic studies

  • t(11;22)(p13;q12)

 

Differential diagnosis                     

  • PNET
    • Desmoplastic stroma: in the classical type is absent
    • Intracytoplasmic glycogen
    • CD99: typically positive (membranous)
    • FlI1: positive
    • Cytokeratin and EMA: positive
  • Alveolar rhabdomyosarcoma
    • Nuclear moulding is not a feature
    • Tigroid background (Giemsa stains)
    • Smooth muscle actin and Myo-D1: positive
    • Myogenin: positive
  • Neuroblastoma
    • Younger children
    • Neuropil
    • Frequent rosettes
  • Other small round cell tumours, depending on the site of origin: pancreatoblastoma, pancreatic neuroendocrine tumours , hepatoblastoma and Wilms’ tumour

 

Main points

  • Some authors advent a probable origin from a primitive mesothelial cell-“Mesothelioblastoma”, based on the immunoexpression to desmin, WT1, vimentin and cytokeratin’s, by both mesothelium and this entity
  • Extremely aggressive neoplasm: average survival less than three years
  • Weak response to chemotherapy
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