Definition
- Essential:
- Biphasic morphology with a dominant desmoplastic leptomeningeal component admixed with a neuroepithelial component containing astrocytic cells only (DIA) or containing astrocytes and neuronal cells (DIG) AND (for unresolved lesions)
- Methylation profile of DIG/DIA OR
- BRAF or RAF1 mutation or fusion, occurring in the absence of homozygous deletion of CDKN2A and/or CDKN2B
- Desirable:
- Tumour with a cystic component and a solid portion, with leptomeningeal involvement, usually attached to the dura
- Infantile onset (typically at < 24 months)
- OLD
- A benign glioneuronal tumour composed of a prominent desmoplastic (growth of fibrous tissue around disease) stroma with a neuroepithelial population restricted either to….
- Desmoplastic infantile astrocytoma (DIA): neoplastic astrocytes OR
- Desmoplastic infantile ganglioglioma (DIG): neoplastic astrocytes together with a variable mature neuronal component +/- aggregates of poorly differentiated cells
Numbers
- Children
- 0.3% of all CNS tumours
- 1.25% of all paediatric brain tumours
- Median age is 6 months
- Male to female 1.5: 1
Localisation
- Supratentorial
- >1 lobe
- Frontal/parietal > temporal > occipital
Origin
- Unknown
- Small cells on the slide are primitive that expresses both glial and neuronal protein component and might be the origin of the tumour → ? Come from specialized subpial astrocyte of the developing brain
Clinical features
- HCP
- Short duration and include increasing
- Head circumference
- Tense and bulging fontanelles
- Lethargy
- Setting-sun sign
Grading
- WHO Grade 1
Genetic
- BRAF mutation
- BRAF V600E mutations
- RAF1 mutations
- Lack the CDKN2A and/or CDKN2B homozygous
- Which is present in PXA
Radiology
CT
- The solid portion of these large masses is typically slightly hyperattenuating and usually located along the cortical margin of the mass.
- CT+C: these masses usually enhance intensely and may demonstrate a dural tail
- Calcification is variably reported, uncommon in some series and up to 50% in others.
MRI
- Solid component: frequently dural based
- T1: iso/hypointense to brain parenchyma
- T2: iso/hypointense to brain parenchyma
- T1 C+ (Gd)
- Intense enhancement
- A dural tail may be seen
- Cystic component
- T1+C: Non enhancing
Images
Histopathology
Macroscopic
- Large cystic lesion involving superficial cerebral cortex and attached to leptomeninges (dura)
- Large (measuring as much as 13 cm in diameter)
- Have deep uniloculated or multiloculated cysts filled with
- Clear fluid
- Xanthochromic fluid
Microscopic
- Slow-growing superficial neuroepithelial tumour composed of a dominant desmoplastic leptomeningeal component and most often containing a variable poorly differentiated neuroepithelial component.
- Desmoplastic leptomeningeal component:
- Consist of a mixture of fibroblast like spindle-shaped cells with a wavy pattern with abundant connective tissue
- Gemistocyte: Greek γέμιζω (gemizo), meaning 'to fill up' is a swollen, reactive astrocyte. These cells usually appear during acute injury; after that, they gradually shrink in size
- Ki-67 index <2%
Immunophenotype
- Leptomeningeal desmoplastic component-fibroblast like cells express:
- Vimentin: positive
- GFAP: positive
- SMA: variable
- Neuroepithelial component:
- GFAP: positive
- Neuronal markers (e.g. synaptophysin): positive if ganglion cells present
Management
- Surgery
- Challenging:
- Size
- Location
- 40% of cases may require adjuvant chemotherapy and possibly radiotherapy in older children
Prognosis
- Long term survival in patient with gross total resection
- Patients with disseminated disease are not altogether uncommon
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