Diffuse astrocytoma

Clinical:

  • A 43 years old lady
  • No known medical illness
  • Presented with recent onset seizures
  • No body weakness
  • No constitutional symptoms

MRI findings:

  • MRI brain in (A) T2WI, (B) FLAIR, (C) T1WI and (D) T1+Gadolinium sequences
  • There are intra-axial masses identified within the right frontotemporal region (yellow arrows) involving the right basal ganglia
  • These masses appear hypointense on T1, hyperintense on T2 and slightly hyperintense on FLAIR sequences. No enhancement on post contrast images.
  • No blooming artefact is identified on HEMO¬† sequence (E) to suggest presence of blood product/ calcification.
  • No area of restricted diffusion is observed on DWI/ADC sequences (F &G).
  • There is minimal perilesional vasogenic oedema, effacement of the right lateral and 3rd ventricles. Compression effect causing distortion of the midbrain is also seen.
  • Midline shift to the left of 1.0 cm is observed. No hydrocephalus observed.

HPE findings:

  • Macroscopy: specimen labelled as brain tumour consists of multiple pieces of whitish tissue
  • Microscopy: sections from the specimen shows fragments of tumour tissue composed of moderately cellular cells in a background of loosely structured microcytic stroma. The tumour cells exhibit mild nuclear atypia which are enlarged, cigar-shaped nuclei with irregular hyperchromatic nuclei and scanty cytoplasm. No mitosis, necrosis or microvascular proliferation seen. No normal brain tissue identified in this biopsy.
  • Immunohistochemical studies shows the tumour cells are GFAP positive and Ki67 proliferative index 4%.
  • Interpretation: Diffuse astrocytoma, WHO Grade II.

Diagnosis: Diffuse astrocytoma.

Discussion:

  • Also known as Grade II astrocytoma or low grade astrocytoma
  • It is a primary brain tumour of astrocytic origin with intrinsic tendency for malignant progression, degeneration into anaplastic astrocytoma.
  • A well-differentiated but infiltrating neoplasm with slow growth pattern
  • Majority presented between 20-45 years old
  • Seizure is the most common presenting feature
  • Supratentorial location in 2/3 of cases and infratentorial in 1/3 of cases
  • Variable in size
  • It may extend into cortex, 20% involve deep gray matter structures such as thalamus and basal ganglia
  • NECT: Ill-defined hypodense/isodense mass, calcification in 20% of cases, cystic component is rare.
  • CECT: no enhancement or very minimal
  • T1-MRI: homogenous hypointense mass which may expand white matter and adjacent cortex, appears circumscribed but infiltrates adjacent brain, calcification and cysts are uncommon
  • T2-MRI: homogenous hyperintense mass with infiltration to adjacent brain, may expand adjacent cortex, hemorrhage and surrounding oedema are rare
  • FLAIR: homogenously hyperintense mass
  • DWI: no restricted diffusion
  • T1+Gadolinium: usually no enhancement, enhancement suggests progression to higher grade
  • MRS: high choline, low NAA typical but not specific
  • Median survival: 6-10 years.
Author: radhianahassan