Case Number : Case 2706 - 19 November 2020 Posted By: Saleem Taibjee

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. 

DPN with a clonal phenomenon.

What’s a “clonal phenomenon” please? 

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

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.

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.

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