Case Number : Case 2776 - 25 February 2021 Posted By: Saleem Taibjee

Melanoma with invasion

Agree.

Only some of the images were included. I am attaching all the images below.

Spitz Nevus.

I would like to see HMB45, P16 and Ki67 because of intradermal component

Many Kamino’s bodies. Simmetry. The pagetoid growth appearance could be due to the many dermal papillae in between retie ridges. Desmoplasia. 

Difficult, but it could be an Atypical Spitz Tumor. 

Pagetoid desmoplastic spitz, atypical sptiz or spitzoid melanoma, The nuclei appear uniform and there seems to be some maturation towards the base, therefore, favouring pagetoid/desmoplastic spitz or atypical spitz tumor over melanoma. 

I would favor an Atypical Spitz tumor.

Spitz nevus

Thanks for the comments.

This is a referral case to me from a neighbouring hospital in 2019. I also shared it with Richard Carr at the time, and our consensus was Spitz naevus. It is symmetrical, well-demarcated, nice Kamino bodies, focal upward spread at the central aspect only. The nesting nicely dissipates at the deep aspect, with no dermal mitotic activity. Although not shown, Ki67 was low. Of course, one always feels a bit more uncomfortable making a diagnosis of benign Spitz in an older patient. However, it is a thin lesion, hence the stakes were not so high here (most unlikely to have any significant metastatic potential even if atypical as I note some of you favour as designation). But, of course, age itself should not automatically make us push such a lesion into an atypical category if other features are generally reassuring. But these are always difficult cases, and it helps to share such cases. It is also worth considering requesting a couple of levels (but not before cutting any required immunos or spare unstained sections). I have come across at least one memorable case in which the initial levels were a close mimick of Spitz naevus, but additional levels were unequivocal melanoma.

I think if encountering such a lesion now, a couple of years later, I would probably also 'routinely' request IHC for BRAFV600E and PRAME, just as a signal / screening for a possible 'wolf in sheep's clothing' i.e. positive BRAFV600E would be generally unexpected if Spitz naevus (and therefore warrant a closer look for a possible 'spitzoid' (but not true Spitz lineage) superficial spreading melanoma). Similarly a strong positive PRAME would also make me hesitate.

BW

Saleem

There is a lesson for me in this - avoid "keyhole histopathology"!  In other words don't commit to an opinion until you have seen all the available information.

In the website's early years Phillip McKee's original concept for the Spot Diagnoses was to try and encourage participants to reach an opinion based on their assessment of a single photomicrograph.  As long as the field chosen contained diagnostic features this was often possible.  However, of course this was a very artificial concept and not a reflection of the real world, or of good practice.