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 2361 - 10 July 2019 Posted By: Iskander H. Chaudhry

Please read the clinical history and view the images by clicking on them before you proffer your diagnosis.
Submitted Date :
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73 M Left forearm biopsy (excision) Pigmented
lesion - recent change


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vincenzo

Posted

Desmoplastic Melanoma. Is pic8 and last pic S100 instead MelanA?

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Victor Delgado

Posted (edited)

Desmoplastic melanoma is a good thought, however I would like to include a few differentials diagnosis as melanocytic nevus with perineural differentiation and desmoplastic melanocytic nevus.   This one is a small lesion, a little bit asymetrical but well circunscribed, epithelioid and spindle - dendritic melanocytes, maduration at the deep portion and some kind of mucinous material intermigled. IHC is similar for S100, Melan A and HMB45, so I'll add P16, EMA and Glut1. Nice case, thanks for sharing.

Edited by Victor Delgado
p16

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IgorSC

Posted

5 hours ago, vincenzo said:

Desmoplastic Melanoma. Is pic8 and last pic S100 instead MelanA?

Agree. There´s an inequivocal "in situ" melanoma and the desmoplastic dermal component must be of a invasive desmoplastic melanoma, pure type.

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Dr. Richard Carr

Posted

Occam's razor suggest MIS and partly desmoplastic invasive melanoma (would be nice to see S100).

I was a little confused by labels as S100 is nuclear (and cytoplasmic) and MelanA is cytoplasm only. Initially I thought there may be focal weak nuclear here but on balance I think these all show just cytoplasmic so probably labelled correctly and commensurate with partly desmoplastic MM.

Don't forget MelanA diffuse strong / S100 weak/negative is highly characteristic of the "blue" group (although not quite 100% specific not far off).

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Admin_Dermpath

Posted

Dear all thank you. So all the images are of Melan A. It was difficult case and consensus was on the junctional component representing a melanoma in situ and the dermal component at least atypical with some suggestions of desmoplastic melanoma. The clinicians treated it as such (the latter)! Best wishes Iskander

 

 

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