Corpus callosal SOL with differential diagnosis including lymphoma & intermediate grade glioma.

Stereotactic biopsy revealed two cores of brain tissue infiltrated by scattered neoplastic astrocytic cells displaying mildly pleomorphic hyperchromatic nuclei with no mitotic figures and separated by fibrillary background with prominent micro cystic spaces. No tumor necrosis or vascular endothelial proliferation detected.

Immuno-histochemical staining:

• GFAP: Diffuse positive staining.
• LCA: scattered mature lymphocytes showing positive staining. Neoplastic cells were negative excluding the possibility of lymphoma.
• Ki67: Few scattered cells showed positive nuclear staining.
• Proliferation index2%.

Final diagnosis:- Diffuse astrocytoma, WHO grade II.

Note: As part of the current WHO classification of CNS tumors both IDH mutation status and 1p19q status (if IDH positive) should be obtained for correct classification.