Case Number : Case 2936 - 07 October 2021 Posted By: Saleem Taibjee

I think this is a second primary melanoma.  Looks as though there is some superficial invasion.

Agree with Richard. This is a radial stage, of a superficial spreading type melanoma, instead of a lentigo maligna type, as expected in this location. It’s initially invasive, but not with a penetrating intradermal nodule. 

Superficial Spreading Melanoma.

agree superficial spreading melanoma

it is MM as it is spreads down the hair follicles 

So it seems that there is a clear consensus from the respondents on melanoma....

However, although there are some worrying features here, I was not sure there is enough for outright melanoma. It is only a 3mm lesion!

I preferred to sit on the fence here, and a MELTUMP/STUMP designation, but advising a conservative re-excision given the close margins.

Of further interest is the immunohistochemistry...

This indicated expression of ROS-1 and lended weight to a possible underlying ROS-1 fusion as a driver, and BRAFV600E negative, and thus true Spitz lineage. For what it's worth, PRAME was negative, although I would not trust it in this situation. p16 appears to be preserved, Ki67 low.  See below.

It would be interesting to know if the immunos would alter the opinions of any of the respondents? For me at least, melanocytic pathology is becoming an increasingly grey area!

BW

Saleem

ROS-1 fusion makes it a Spitzoid lesion. Given it retains p16 would you classify this as a simple Spitz Nevus or an Atypical Spitz Tumor?

18 hours ago, msofopoulos said:

ROS-1 fusion makes it a Spitzoid lesion. Given it retains p16 would you classify this as a simple Spitz Nevus or an Atypical Spitz Tumor?

Agree. I have the same thought

• I classified as Atypical Spitz Tumour. I would not rely upon p16. Certainly it is more worrying if there is loss (and might imply p16 deletion at the molecular level), but there are still worrying features in this case, including the demographic.