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