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Solitary Fibrous Tumour

Summary

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  • Rare mesenchymal neoplasm of fibroblastic origin
  • Can occur in various anatomical locations, most commonly pleura
  • Typically presents as a slow-growing, well-circumscribed mass with variable imaging features

Pathophysiology

  • Derived from CD34-positive fibroblastic cells
  • Characterised by NAB2-STAT6 gene fusion, resulting in STAT6 nuclear expression
  • Majority are benign, but 10-20% may show malignant behaviour

Demographics

  • Can occur at any age, peak incidence in the 5th-6th decades
  • No significant gender predilection
  • Most common in pleura, but can occur in various extrapleural sites (e.g., meninges, orbit, soft tissues)

Diagnosis

  • Often asymptomatic, discovered incidentally
  • Symptoms depend on location and size:
    • Pleural: dyspnea, chest pain
    • CNS: headache, seizures, focal neurological deficits
    • Soft tissue: painless mass
  • Diagnosis confirmed by histopathology and immunohistochemistry (CD34, STAT6 positive)

Imaging

  • CT:
    • Well-circumscribed, lobulated mass
    • Heterogeneous enhancement
    • Calcifications in 10% of cases
  • MRI:
    • T1: isointense to muscle
    • T2: variable, often heterogeneous with areas of high and low signal intensity
    • Strong enhancement after gadolinium administration
    • "Flow voids" may be present due to prominent vessels
  • Angiography:
    • Hypervascular lesion with prominent feeding vessels

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  • 63-year-old patient presentd with walking instability.
  • MRI showed an enhancing well-defined extra-axial lesion distorting the right cerebellar hemisphere.
  • Imaging modified from Zhu et al[^1].

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  • A 30-year-old patient presented following a seizure.
  • MRI showed a heterogeneously T2-hyperintense and enhancing lesion over the left frontal pole.
  • The lesion was resected and a solitary fibrous tumour was diagnosed.

Treatment

  • Surgical resection is the primary treatment modality
  • Complete resection associated with better prognosis
  • Adjuvant radiotherapy may be considered for incompletely resected tumours
  • Chemotherapy reserved for metastatic or unresectable disease
  • Long-term follow-up recommended due to risk of late recurrence

Differential diagnosis

Differential Diagnosis Differentiating Feature
Meningioma Dural tail sign on contrast MRI; may calcify; more commonly convexity-based
Schwannoma Eccentric growth along cranial nerve; cystic degeneration common; no "yin-yang" T2 pattern
Hemangioblastoma Large cyst with small enhancing mural nodule; no lobulated solid mass; associated with VHL
Metastatic tumour Often multiple extra-axial or intraparenchymal lesions; surrounding vasogenic oedema
Glioblastoma Infiltrative intraparenchymal mass with ring enhancement and central necrosis; not extra-axial