Grade 2 Astrocytoma Pathology Question

After a GTR the pathology came back as grade 2 astrocytoma. The oncologist appointment is coming and I will know what’s next.

However, the pathology seems a little strange from the research I’ve done.

Has anyone encountered IDH mutation with no mutation in ATRX or TP53 while 1p/19q is not codeleted? Or am I missing something?

Pathology Results:

Final Diagnosis A and B) Brain, right insular tumor, biopsy and resection: - Astrocytoma, IDH1 R132H-mutant, CNS WHO grade 2. Comment FISH testing for 1p/19q is negative for codeletion, diagnostic for astrocytoma in the setting of an IDH1 mutation. FISH testing for CDKN2A/B is negative for homozygous deletion.

Microscopic Description The slides generated for intraoperative consultation are reviewed and the impression is confirmed on permanent sections. Histologic sections demonstrate a hypercellular proliferation of atypical glial cells with moderate nuclear pleomorphism, irregular nuclear contours, and eosinophilic, variable gemistocytic and fibrillary cytoplasm arranged in sheets. No definite mitotic figures are identified. No foci of microvascular proliferation or necrosis are present. Immunohistochemical staining for IDH1 R132H shows diffuse expression. Staining for p53 shows scattered nuclear expression (wildtype pattern) and staining for ATRX shows retained expression (wildtype pattern).