Anaplastic astrocytoma IDH wild-type

Discussion:

Case illustrating an extensive left cerebral hemisphere that has the imaging characteristic of a glioma. The features demonstrated in the last MRI, enhancing foci with restricted diffusion and elevated CBV, favors a high-grade glioma. Spectroscopy was performed at that time (not shown), and was of elevated choline peak and decreased NAA.  

The patient was submitted to a brain biopsy. 

Histology

MICROSCOPIC DESCRIPTION: The sections show features of a moderately cellular glial tumor. Most of the cells appear morphologically astrocytic with elongated, angulated and hyperchromatic nuclei. Occasional tumor cells have round nuclei and perinuclear haloes. Scattered mitoses are seen. No microvascular proliferation or necrosis is present. Sparse calcified deposits are present in the background. The features are consistent with anaplastic astrocytoma. The tumor cells are focally p53 positive. The topoisomerase index is about 10%. IDH1-R132H immunostain is negative. MGMT is also negative (likely methylated). ATRX shows no loss of staining (non-mutated).

  • 1p36: NO DELETION DETECTED
  • 19q13.3: NO DELETION DETECTED 
    • Number of sites scored: 10 
    • Number of cells scored: 200 
    • 1p36/1q25 ratio 0.982 
    • 19q13.3/1p13 ratio: 0.962 
      • REFERENCE CRITERIA: 
        • 1p36/1q25 ratio <0.8 Deletion detected 
        • 19q13.3/19p13 ratio <0.8 Deletion detected 

FINAL DIAGNOSIS: anaplastic astrocytoma (WHO Grade III), IDH wild-type.

Note: Although this tumor is entirely consistent with IDH wild-type molecular subtype, strictly speaking, to conclusively establish this, IDH would need to be sequenced to ensure that a non-IDH1 R132H mutation was present. In practice, an IDH1 R132H negative tumor in an individual over 55-years-of-age makes the possibility of this being IDH mutant remote (<1%), and sequencing is not felt to be necessary by many institutions, and not recommended by the WHO classification of CNS tumors (2016). 

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