Case Number : Case 3042 - 04 March 2022 Posted By: Dr. Richard Carr

Atypical junctional proliferation over a dermal scar - It seems like the junctional proliferation extends past the edge of the scar, suggesting real MIS rather than just recurrence phenomenon.... Previous biopsy/trauma? 

Agree very broad and confluent proliferation suggestive of MMIS. 

No PRAME expression and p16 is retained, so may be a recurrent nevus simulating MMIS. Although, H&E was suspicious for MMIS, as the proliferation seem to go past the scar.

I favoured a mildly dysplastic naevus with rather confluent lentiginous pattern and pseudomelanomatous changes. I guess the important point is to ensure complete removal of this sort of challenging lesion which will garner a range of diagnostic opinions. The lesion lacks significant atypia and even the scatter of pagetoid cells are small with nuclei no larger than keratinocytes and with open chromatin. The multinucleate cell is rather typical of benign lesions. Pagetoid scatter seems to be very typical of melanoma but is clearly not entirely specific and not sensitive either. I'm still finding PRAME quite useful especially when it agrees with my favoured diagnosis!