Case Number : Case 2243 - 17 January 2019 Posted By: Raul Perret

Spindle cells with long cytoplasmic process , myxoid stroma and forming whorls with focal reticular microcysts. To me, this is intraneural reticular perineurioma ( a variant of soft tissue perineurioma). Can do EMA to highlight it.

Confess not seen one like this before but my "1st principles" thought was some variant of perineurioma too!

I´m agree with Reticular (and probably plexiform too) Perineurioma.

BUT... Only after read the comments above (because i was clueless)

I had never seen a case like this. It made me think about something "neural" and perineurioma seems a good diagnosis.

Whorls of thin, long processes(?peri-neural axons in fig2) make me think of perineurioma.  So agree with Colleagues. 

I don’t see true axons in fig 2 but it seems perineural typeIV collagen whorls(left centre field). 

2 hours ago, vincenzo said:

I don’t see true axons in fig 2 but it seems perineural typeIV collagen whorls(left centre field). 

Here are some degenerated axons...

Yes! Thanks Henry!

An Hybrid neurofibroma/perineurioma tumor...

Yes, I called this lesion a myxoid hybrid nerve sheath tumor (perineurioma/schwannoma). We can see the perineurial cells with slender delicate nuclei and long cytoplasmic processes intermingled with shwann cells with triangular nuclei and a more prominent cytoplasm. There are also some vessels with hyalinized walls which are frequent in schwannoma but rarely observed in perineurioma. 

1 hour ago, Raul Perret said:

Yes, I called this lesion a myxoid hybrid nerve sheath tumor (perineurioma/schwannoma). We can see the perineurial cells with slender delicate nuclei and long cytoplasmic processes intermingled with shwann cells with triangular nuclei and a more prominent cytoplasm. There are also some vessels with hyalinized walls which are frequent in schwannoma but rarely observed in perineurioma. 

Thanks Raul ( now I finally get that right!) for the nice case. I am a lumper not a splitter, so in this case, I think I will not push to call it hybrid nerve sheath tumor ( perineurioma/schwannoma). actually your S100 stains highlighted many of those degenerated axons to me, the predominant lesion is just a myoxid reticular perineurioma.  anyway, keep the good work, Excellent case and images!

https://www.semanticscholar.org/paper/Intraneural-reticular-perineurioma-of-the-nerve-Kum-Kim/4b0b939d54f33047bed528e2ee417ea73e23bbd4/figure/3

some of the vessels are also hyalinized/thickened..

14 minutes ago, HENRY said:

https://www.semanticscholar.org/paper/Intraneural-reticular-perineurioma-of-the-nerve-Kum-Kim/4b0b939d54f33047bed528e2ee417ea73e23bbd4/figure/3

some of the vessels are also hyalinized/thickened..

Thanks for sharing Henry, the overall architecture of the tumor presented here may be partly intraneural. Nevertheless, the schwann component was highly abundant and intermixed with the perineurial component (there aren't only axons present, see s100 stain). Note also that the myxoid degeneration seen in the 2 last pictures was focal and that the majority of the lesion had the architecture seen in the first picture, this is important because there is not an overall reticular morphology (I did not even include it in my differential)