Astrocytoma with piloid features in patient with NF1

Discussion:

This case demonstrates aggressive behavior of an astrocytic tumor with piloid features in a patient with known NF1.

At the time this was reported, it was determined to be a pilocytic astrocytoma. Although generally considered low-grade tumors (WHO grade 1) they can behave more aggressively, as is the case here. 

More recently high-grade astrocytoma with piloid features has been described and is defined by its DNA-methylation profile - and as such whether this case is definitely an example of not is uncertain. 

The histology images were reviewed (in 2022) by a neuropathologist who said: 

"Given that this entity is defined by methylation profile, I can't be completely certain that this entity is high-grade astrocytoma with piloid feature.​

It certainly has a piloid appearance. It's also in the most common location. The microvascular proliferation and necrosis is hard to interpret because you can get that pilocytic astrocytomas also. But necrosis is generally present in HGAPF. The lack of mitotic figures is unusual, and that was the case in both resections.  The topoisomerase and cellularity are also low. But ultimately, you can also get HGAPFs that are histologically low grade, so all this could still fit." 

The patient had rapid recurrence and was deemed inoperable and died from the tumor three years after initial diagnosis. 

 

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