Astroblastoma, MN1-altered

Astroblastomas are an uncommon primary neuroepithelial tumours which, along with choroid gliomas of the third ventricle and angiocentric gliomas, are grouped as other neuroepithelial tumours in the 2007 version of the WHO classification of CNS tumours.

Epidemiology

They occur at all ages range from early childhood to 6th decade but are most commonly seen in children, adolescents, and young adults with a mean age between 10-30 years ².  Their Their incidence is estimated to be 0.45-2.8% of all neuroglial tumours ⁴.

Pathology

They are well-demarcated masses with areas of cystic degeneration and necrosis giving it a bubbly appearance. Haemorrhage and adjacent brain infiltration are rare.

Two distinct histological types were reported ⁴:

• low-grade type: well differentiated pattern and favourable prognosis
• high-grade type: more anaplastic features with short postoperative survival

Histology

Common histologic finding is perivascular rosettes similar to the ependymomas.

Location 

Almost always supratentorial and peripheral.

Radiographic features

They are large, peripherally located, supratentorial lobulated solid cystic masses with little if any associated vasogenic oedema. Multiple cysts give it a bubbly appearance. Calcification is very common and seen in 85% of cases, and usually in a punctate pattern.

MRI

• T1: iso- to hypointense
• T2/FLAIR: heterogeneously hyperintense
• T1 Gd (C+): heterogeneous enhancement

Treatment and prognosis

Surgical resection is treatment of choice with adjuvant radiation therapy and chemotherapy reserved for high-grade lesions. Unless being a high grade lesion recurrence after surgical resection is uncommon ⁴. Metastasis is also very rare.

Differential diagnosis

Possible imaging differential considerations include:

• hemispheric ependymoma
• atypical teratoid/rhabdoid tumour
• oligodendroglioma
  • nodular calcifications instead of punctate calcifications ²
• pleomorphic xanthoastrocytoma
• dysembryoplastic neuroepithelial tumour (DNET)