Clinical History
This 43-year-old patient presented with complaints of worsening right-sided weakness. Neuroimaging demonstrated a 1.8 x 1.5 x 1.5 cm heterogeneous appearing mass involving the left frontoparietal lobe at the site of a previously resected WHO grade 2 oligodendroglioma with codeletion of 1p/19q detected by fluorescence in-situ hybridization (FISH) 10 years ago.
On hematoxylin and eosin stained sections the lesion showed a relatively well-circumscribed interface with surrounding more normal appearing but gliotic brain tissue that contained occasional Rosenthal fibers. Focal tumor necrosis was present. No microvascular proliferation or significant increase in mitotic activity was seen. The proliferative fraction was 2-3% as estimated by KI67 immunostain. No codeletion of 1p/19q was detected by FISH in the recurrent/residual neoplasm.
What is the most likely diagnosis based on the provided images of H&E GFAP, reticulin, IDH1 R132H and ATRX stained sections? (Images below)
Correct Answer:
- The provided images demonstrate the presence of a glial neoplasm with extensive mesenchymal differentiation. Alternating areas of GFAP-positive/reticulin-negative neoplasm and GFAP-negative/reticulin-positive areas are present. The lesion is immunopositive for IDH1 R132H mutant protein and shows retention of nuclear staining for ATRX.
- In the context of this patient’s clinical history, oligosarcoma is felt to be most likely. Such lesions may show copy number neutral loss of heterozygosity (LOH) for 1p/19q that is not detectable by FISH. These neoplasms are felt to be of high grade.
References:
- Suwala AK, et al. Oligosarcomas, IDH-mutant are distinct and aggressive. Acta Neuropathol. 2022 Feb;143(2):263-281. doi: 10.1007/s00401-021-02395-z. Epub 2021 Dec 30. PMID: 34967922; PMCID: PMC8742817.
- Landvater R,et al. Sarcomatous transformation of IDH-mutant astrocytoma matching to methylation class oligosarcoma following embolization, a case report. Acta Neuropathol Commun. 2024 Dec 20;12(1):196. doi: 10.1186/s40478-024-01908-7. PMID: 39707480; PMCID: PMC11662476.
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