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In this section we have spot diagnoses posted on a daily basis since June 2010, now over 1700! You can review the archived cases and read the suggested diagnoses by users and the final comment by Dr Uma Sundram, the Editor-in-Chief and main spot diagnosis host. Case are uploaded each week day by 10 a.m. UK time with the correct diagnosis will generally be posted at 8 p.m. UK time. Why not view the most recent spot diagnosis and proffer a diagnosis?

Case Number : Case 2278 - 7 March 2019 Posted By: Raul Perret

Please read the clinical history and view the images by clicking on them before you proffer your diagnosis.
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47y old man, 4 cm buttock tumor


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Alex-Ventura-Leon

Posted

Low-Grade Fibromyxoid Sarcoma is my spot.

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Why not a low grade dedifferentiated liposarcoma? There is an atypical lipoblast in last fig.

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vincenzo

Posted (edited)

...if deeply seated of course...

Edited by vincenzo

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Dr. Mona Abdel-Halim

Posted

I also though of dedifferntiated liposarcoma

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The location would be very unusual for dedifferentiated liposarcoma. Strictly speaking, lipoblasts are characterized by fat vacuoles indenting the nucleus like scalloping. So I am not convinced that's a lipoblast. 

The "lipoblasts " and other large cells would be very unusual for low-grade fibromyxoid sarcoma, but MUC4 would help.

The orange stained collagen is really unusual. But I think Dr. Carr explained one time why it looks so funny. But I am still not accustomed to look at that. Maybe some kind of atypical fibrous histiocytoma? How deep is this lesion?

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Agree, neurofibroma.

But the tumor is also positive for EMA with a  long cytoplasmic dendritic pattern. CD34 displays a whorling  pattern. Neurofibroma is usually negative for EMA. So there is another component in the tumor, namely perineurioma I think.

In summary:

Hybrid tumor: NF and perineurioma?

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Dr. Richard Carr

Posted

The French use Saffron in the H&E stain. Very chic! Nice fingerprint pattern on CD34.

J Cutan Pathol. 2011 Aug;38(8):625-30. doi: 10.1111/j.1600-0560.2011.01700.x. Epub 2011 Apr 4.

Distinguishing neurofibroma from desmoplastic melanoma: the value of the CD34 fingerprint.

We have observed 'fingerprint' immunopositivity in association with perineurioma and neurofibroma. A fingerprint consists of delicate, elongated areas of positive labeling that fall between collagen bundles, thereby creating a whorled configuration that is reminiscent of a human fingerprint. At present, the differential diagnosis between early desmoplastic melanoma and neurofibroma remains challenging in a subset of cases because of overlapping histopathological and immunohistochemical features. To assess whether fingerprint CD34 reactivity could be contributory in this context, we stained 50 desmoplastic melanomas and 50 neurofibromas with CD34. Fingerprint CD34 labeling was present in greater than 30% of the proliferation in 96% (n = 48) of neurofibromas and in only 4% (n = 2) of desmoplastic melanomas. Over two-thirds of the neurofibromas exhibited a CD34 fingerprint involving more than 60% of their surface area. In the two cases of desmoplastic melanoma that showed CD34 fingerprint positivity, the staining was patchy and involved less than 60% of the tumor. In partially staining neurofibromas, areas without a CD34 fingerprint tended to occur in central lobular areas. We conclude that CD34 fingerprint immunoreactivity is useful in distinguishing neurofibroma from early desmoplastic melanoma, especially if the fingerprint involves more than 60% of a tumor's cross-sectional area.

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Raul Perret

Posted

Thanks for the article Richard. This is actually a hydrid nerve sheath tumor (Schwannoma/Perineurioma) showing focal degenerative atypia. This is definetely and underrecongnized entity. I have made a small table that recapitulates the main features that we use to diagnose hybrid nerve sheath tumors. This is based on the two biggest series reported to date. Hope is useful.

Hybrid Nerve Sheath tumors.tif

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Thanks for your many learning points, Richard and Raul!

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