Alveolar soft part sarcoma

Clinical features

  • Affects children and young adults
  • Indolent tumour
  • High aggressiveness
  • Deep soft tissue of oral cavity, pharynx, mediastinum, thigh/leg
  • Female predominance
  • Vascular invasion and metastasis are frequent
  • No specific clinical or
  • No clinical or histopathological features  that are reliably predictive of disease course

 

Cytopathology

  • Haemorrhagic smears
  • Low to moderate cellularity
  • Sheets or single cells
  • Numerous bare nuclei
  • Large epithelioid cells with abundant finely granular cytoplasm
  • Large nuclei with prominent nucleoli
  • Nuclear pseuinclusions
  • Rarely  extracellular crystalloid (PAS-positive diastase resistant) bodies

 

Histochemistry

  • PAS (+) diastase-resistant granular to crystalline cytoplasm material

 

Immunocytochemistry

  • FE3- nuclear
  • MyoD1 : negative
  • Vimentin: negative
  • HMB45: negative
  • S100 protein : negative
  • CD 34: negative
  • Calretinin: Positive (46%) (2)

 

Electron microscopy

  • Rhomboid intracytoplasmic membrane-bound crystals

 

Genetic studies

  • t(X;17)(p11.2;q25)

 

Differential Diagnosis

  • Granular cell tumour
    • benign lesion
    • Granularity of cytoplasm is more coarse
    • TFE3- positive in 91%  (2)
    • Calretinin: Positive
    • S100: Positive
  • Paraganglioma
    • Chromogranin: positive
  • Renal cell carcinoma Xp11.2 associated
    • Absence of renal mass

 

Main points

  • Poorly responsive to adjuvant chemotherapy.
  • Surgical excision is the treatment of choice
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