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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 2706 - 19 November 2020 Posted By: Saleem Taibjee

Please read the clinical history and view the images by clicking on them before you proffer your diagnosis.
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66-F, Pigmented lesion left posterior thigh - ?melanoma


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I think there are three partners in this combined melanocytic enterprise: 

1) a conventional nevus, intradermal and congenital type

2) a DPN, the expected business partner

3) but there is a third wheel...a melanoma in situ.

Not too sure about this, but it’s my spot. 

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DR NADINE BURKE

Posted

low power wedge. and other features of DPN.

But junctional component concerns me with some upward migration. this is difficult. I would def ref for an opinion.

so DPN like melanoma

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Saleem Taibjee

Posted

This was a tricky case. Histology shows a compound melanocytic proliferation which comprises a junctional component with somewhat 'active' epithelioid nesting. Possible focal cells above the basal layer. The dermal component is wedge-shaped, and comprises epithelioid and fusiform cells in nests and fascicles with associated conspicuous melanophages. At the periphery of the tumour some of the melanocytes take on a dendritic morphology. The majority of tumour cells, however, comprise vesicular nuclei with a single central nucleolus. There is a degree of cellular pleomorphism. However, no dermal mitoses were identified.

Beta-catenin showed nuclear positivity throughout (both junctional and dermal components). Ki67 is very low – see below.

I certainly had clinical suspicion for melanoma when I saw this patient, and noting the age of the patient. I did obtain second opinions on this case (including Eduardo Calonje), and the majority view was to regard as atypical deep penetrating naevus / melanocytic tumour of uncertain malignant potential. We did not undertake any further re-excision since the lesion appeared well-excised. However, we are keeping her under follow-up, not problems thus far.

On submitting the case this week, it led me to read the chapter from Busam et al’s excellent book “Pathology of melanocytic tumours”. I note that DPN is usually an intradermal lesion, but not infrequently it can be associated/combined with another lineage to account for an associated junctional component. A degree of cytological atypia is allowable within DPN, and should not lead to an overdiagnosis of malignancy.

I now also note that from the images in my case that the melanophages are asymmetrically distributed. As Vincenzo points out, this leads credence to a combined naevus element, in which melanophages are less evident within a central-right zone which may represent a more conventional naevocellular element. I’m not convinced that there is sufficient for melanoma-in-situ however, but this is a very subjective case. Unfortunately I don’t have routine access to molecular studies which might be illuminating in this case.

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Saleem Taibjee

Posted

I don't seem to be able to add the immunohistochemistry images directly, but will ask the adminstrative team to do this at a later time.

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Admin_Dermpath

Posted

On 25/11/2020 at 07:34, Saleem Taibjee said:

I don't seem to be able to add the immunohistochemistry images directly, but will ask the adminstrative team to do this at a later time.

Sorry for the delay as there were some technical issues - now resolved and Immuno posted

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