Case Number : Case 3006 - 13 January 2022 Posted By: Saleem Taibjee

Not easy this one. I think this is a pagetoid compound Spitz nevi. Looking for HRAS alteration or kinase-fusion (Alk, ROS1 or NTRK) would be of great help.

PERSISTENT/TRAUMATIZED NEVUS. 

Atypical nests are limited art the cicatricial area. Abrupt border together with the scar below. Kamino bodies (maybe this was/is a Spitz nevus ). 

Spitzoid features and scarring. May be traumatized spitz nevus. 

Lots of Kamino bodies. I am thinking of Spitz

Yes, there seems to be good agreement here on Spitz lineage. I did find this a tricky lesion, particularly given the Pagetoid spread, fibrosis and inflammation. But the lesion is small and well-demarcated.

I am increasingly requesting additional immuno in such cases. A single IHC stain will not provide a definitive answer, but as a panel we can add to the pieces of the puzzle and help to either substantiate our impression from the H&E in subjective cases, or see if there are any alarm bells/signals. In particular, BRAFV600E should be negative (as it was in this case) if Spitz lineage (and thus rules out a Spitzoid 'conventional' superficial spreading melanoma mimic). PRAME was also negative. Furthermore NTRK was nicely positive in this case, supporting Spitz lineage.

There is undoubtedly some over-diagnosis of melanoma occurring, and I think that these are the sorts of cases which might be diagnosed as early melanomas at some centres, the clinician then congratulating themselves on picking up that early melanoma, but the patient left with a label that he/she has to live with.

It can definitely help to share such cases amongst colleagues. It makes it easier to 'come off the fence'. The clear consensus was Spitz with some atypical features, perhaps reflecting trauma, but falling short of criteria for malignancy. 

BW, Saleem

I'm late to the party...

Saleem, could you please share which NTRK IHC you use?

I order stains from Neogenomics in the USA - they have Pan-TRK (clone EPR17341).

Thanks!

Jacob.