Case Number : Case 1554 - 09 June Posted By: Guest

Spitzoid tumour of uncertain malignant potential.

Atypical spitz tumor. There are some mitotic figures (one atypical to my eyes) location is infrequent but just guiding myself with the images I would favour benign behaviour. My reasons for favouring benign are: symmetric lesion, scarce mitotic activity, quite superficial, absence of associated inflammatory infiltrate, pushing borders not infiltrative, absence of ulceration, patient less than 10 years old. Worrying features: atypical mitosis, quite cellular. 

Agree with an atypical spitzoid neoplasm. I'm thinking of a BAP1-oma ( Wiesner's Nevus ). There are large epithelioid pink cells with sharp borders growing in an expansile nodule, pushing apart residual banal nevus. 

I agree this is most likely an epithelioid atypical spitz tumour, and could be a BAPOMA. There is a sharp demarcation between the non-epithelioid periphery and the expansile central nodule, almost clonal.

Raul, I learned that an infiltrative lower border favours spitz, whereas a pushing lower border favours melanoma. (McKee pages 1181 and 1185). My interpretation of the pictures is that the lower border is infiltrative, so we reach the same conclusion but for different reasons. On the other hand the epidermis shows consumption rather than hyperplasia, so that is an adverse factor. Maybe its a MELTUMP!

I am no worried about this lesion. I think this is a compound Spitz nevus. The mitotic figure is superficial and I don´t see any other atypical features in this lesion. I also think that the compound nature of this lesion argues against Bapoma.

Hello Charlie (and welcome) as everything related with spitz tumors there is some overlap and contrast in some of the criteria for benign (common spitz) vs atypical Spitz vs Spitzoid melanoma. I recommend you this article in table 2 you can see the extent  of variability (including infiltrative vs pushing for spitz). A pushing border makes me favour benign because it is what I have seen more frequently in lesions with good prognosis. Anyway, I was also thinking when I first saw the pictures if kamino bodies are present (which would incline the balance even more to the benign spectrum) maybe Arti will give us her opinion later. 

I think those are colloid bodies.  I liked your first report Raul! i.e. AST of low risk (especially given age). Could look for all the fusions etc (ROS, ALK, p16, BRAF, BAP etc).

Nothing like a funny Spitz to elicit a great discussion!

Yes, I called this an Atypical Spitz too, very low risk and highly likely in behave in a benign fashion.

 If one follows the Spatz criteria for stratifying childhood atypical Spitz tumours, this lesion has a score of 0.

The lesional symmetry, paucity of mitosis (there was only 1 superficial mitosis in the lesion) and lack of significant atypia were all reassuring. To me, the concerning findings were the expansile nature with epidermal consumption and lack of maturation.  With regards to Charlie and Raul's discussion, I have always regarded infiltrative rather than pushing lower margins as a sign of architectural maturation in Spitz. However, in this paper by Gerami et alhttp://www.ncbi.nlm.nih.gov/pubmed/24618612, it was shown that although maturation was one of the important criteria for not labelling cases as melanoma by expert dermatopathologist, there was no link between maturation and clinical out come in their cohort of atypical Spitz tumours. (also many ASTs have dumbbell shaped pushing margins). Likewise, epidermal consumption also did not show association with clinical behaviour. The features most associated with worse outcome were frequent and deep mitoses, lesional asymmetry, high grade atypia and ulceration; none of which are present in this case.

I admit that I did not do a BAP1 stain, but since many of you have raised this possibility, will do this now. In my mind, BAPOmas tend to be purely dermal lesions, but I suppose that is not absolute!

Thanks for all your comments and also thanks to our paediatric pathologist, Dr Jo Mcpartland for sharing this case with me.