Neurosurgery notes/Tumours/Mesenchymal non meningothelial tumours

Mesenchymal non meningothelial tumours

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Soft tissue tumors
Chondro-osseous tumors

General

  • Mesenchyme is derived from mesoderm. The mesenchyme has few cells but with a lot of ground substances around it

Classification

  • Soft tissue tumors
    • Fibroblastic and myofibroblastic tumors
      • Solitary fibrous tumor
    • Vascular tumors
      • Hemangiomas and vascular malformations
      • Hemangioblastoma
    • Skeletal muscle tumors
      • Rhabdomyosarcoma
    • Uncertain differentiation
      • Intracranial mesenchymal tumor, FET-CREB fusion-positive
      • CIC-rearranged sarcoma
      • Primary intracranial sarcoma, DICER1-mutant
      • Ewing sarcoma
  • Chondro-osseous tumors
    • Chondrogenic tumors
      • Mesenchymal chondrosarcoma
      • Chondrosarcoma
    • Notochordal tumors
      • Chordoma (including poorly differentiated chordoma)

Definition

  • Benign and malignant mesenchymal tumours originating in the CNS, with terminology and histological features corresponding to their soft tissue and bone counterparts.

Numbers

  • Benign
    • Various forms of lipoma account for only 0.4% of all intracranial tumours,
    • The other benign mesenchymal tumours are even rarer.
  • Malignant
    • Sarcomas accounted for < 0.1-0.2% of the intracranial tumours
      • The most common tumour types include fibrosarcoma and undifferentiated pleomorphic sarcoma / malignant fibrous histiocytoma (MFH)
  • Can occur at any age.
    • Children: Rhabdomyosarcoma
    • Adult:
      • Undifferentiated pleomorphic sarcoma / MFH
      • Chondrosarcoma usually manifest in adults.
    • No obvious sex predilection.

Localization

  • Tumours arising in meninges are more common than those originating within CNS parenchyma or in choroid plexus.
  • Cranial
    • Supratentorial
      • Most mesenchymal tumours are supratentorial
      • Chondrosarcomas involving the CNS arise most often in the skull base
      • Midline: (ant. corpus callosum, quadrigeminal plate, suprasellar & hypothalamic regions, and auditory canal)
        • Benign mesenchymal lesions,
        • Intracranial lipomas
      • Osteolipomas have predilection for the suprasellar/interpeduncular regions
      • Intraventricular and tuber cinereum lipomas are rare
    • Infratentorial
      • Rhabdomyosarcomas are more often infratentorial
  • Spinal cord
    • Conus medullaris-filum terminale
    • Thoracic level.
      • Epidural space
        • Most spinal lipomas (in particular angiolipomas)

Origin

  • Normally are derived from the neuroectoderm craniospinal meninges, vasculature, and surrounding osseous structures
    • Either develop
      • Directly: mesenchymal structures (e.g. bone, cartilage, and muscle)
      • Indirectly: reversion to a more primitive stage of differentiation.
  • Congenital malformation rather than true neoplasms
    • Lipomas within the CNS + partial/complete agenesis of the corpus callosum and spinal dysraphism with tethered cord
    • Intracranial rhabdomyosarcoma

CNS WHO grading

  • Range from benign neoplasms (WHO grade I) to highly malignant sarcomas (WHO grade IV).

Aetiology

  • Irradiation, several years after
    • Intracranial fibrosarcoma,
    • Undifferentiated pleomorphic sarcoma / MFH,
    • Chondrosarcoma,
    • Osteosarcoma
  • Post-trauma/surgery
    • Intracranial and spinal fibrosarcoma
    • Undifferentiated pleomorphic sarcoma / MFH
    • Angiosarcoma
    • Desmoid type fibromatosis
  • EBV in immunocompromised pts
    • Intracranial smooth muscle tumours

Genetic profile

  • Meningeal-based Ewing sarcoma / peripheral primitive neuroectodermal tumour have shown the typical EWSR1 type rearrangements
  • Intracranial cartilaginous tumours
    • Maffucci syndrome
    • Ollier disease
  • Lipomas with encephalocraniocutaneous lipomatosis osteosarcoma with Paget disease.

Histopathology

  • Macroscopic: Depends entirely on their differentiation
    • Lipomas are bright yellow, lobulated lesions.
      • Epidural lipomas: delicately encapsulated and discrete
      • Intradural lipomas: intimately attached to leptomeninges and CNS parenchyma.
    • Chondromas
      • Demarcated,
      • Bosselated,
      • Greyish-white,
      • Translucent,
      • Large, dural-based masses indenting brain parenchyma.
    • Meningeal sarcomas
      • Firm in texture and
      • Invade adjacent brain
    • Intracerebral sarcomas
      • Well delineated,
      • Parenchymal invasion
    • Sarcomas cut surface
      • Typically firm and fleshy;
      • High-grade lesions often show necrosis and haemorrhage.

Clinical features

  • Variable and non-specific, and depend largely on tumour location.

Radiological

  • Non-specific findings,
  • Lipoma
    • Are diagnostic on MRI
    • T1
      • High signal intensity of fat,
    • STIR
      • Hyperintensity disappears
  • Chondroid and osseous tumours.
    • Speckled calcifications

Prognosis

  • Benign mesenchymal tumours can be completely resected and have a favourable prognosis,
  • Intracranial sarcomas are aggressive and associated with a poor outcome
    • Primary CNS sarcomas are less aggressive than glioblastomas
    • 5-year survival
      • High-grade: 28%
      • Low grade: 83%
    • Despite aggressive radiation and chemotherapy, almost all reported cases of CNS rhabdomyosarcoma have been fatal within 2 years.
    • Spread
      • Common distant leptomeningeal seeding
      • Common systemic metastasis