Case Number : Case 1533 - 10 May Posted By: Guest

Melanoma in-situ.

I dont find this case easy, I would not go for melanoma in situ directly. The dermis looks fibrotic, I would discard a previous surgical excision in the same site. I am afraid this could be recurrent/persistent nevus, if the clinical history is not compatible then it is probably melanoma in situ. 

Cases here are more difficult every week. I agree that Melanoma in situ is the first diagnosis in my mind. I don´t know how to explain the fibrosis on the dermis without a prior ressection. If there´s really no prior ressection, maybe a partial inflammatory regression with a resolving scar like tissue is the answer. I would perform some immunostains to confirm the melanocytic nature of the lesion. I think there´s a high N:C ratio, so I would like to exclude a pagetoid Merkel cell carcinoma as well.

Tricky case! Agree with the comments above. Dermal scarring makes me think of a pseudo-melanoma (provided there has been a previous excision), otherwise an in-situ melanoma, with regression. I think the proliferation is too florid to be associated with simple trauma.

Pseudomelanoma overlying a scar was my first thought. But the history specifically states that there is no known previous bx, so difficult to tie together. Other cause of a dermal scar including trauma and scarring following blistering conditions etc also need to be considered. If all of this is excluded, one would have to call it a melanoma in situ. 

Agree with melanoma in situ if other simulating conditions like recurrent nevus ,prior trauma etc. can be excluded.By the way, i share Igor's comment about difficult cases these days! albeit we love these kind of cases.don't we?

Yes, the harder the better

I learn more when I make a mistake. I think I´m learning more these days, rsrsrs... But I´m enjoying this!!

SAMPUS overlying a scar. Nice suggestion regarding in situ MCC - exceedingly rare but worth a mention on this site. In fact I was also struck be the slightly hyperchromatic nature of the cells (reminded me a little of the acral lentiginous type melanoma cells). Needs to be excised (dependent on clinical / dermatoscopic features). If confirmed to be melanocytic, punch biopsy is medico-legally suspect / unwise to make a reliable histopathological diagnosis - let the clinician know it is their call.

Agree with melanoma in situ.

Agree with all assessments, including that this is a difficult case. We finally decided on atypical intraepidermal melanocytic proliferation (the lesional cells were S100 and Melan A positive). While this could be a persistent/recurrent nevus, melanoma in situ cannot be excluded and the lesion should be completely excised. Certainly the patient/clinician could even consider a MIS-type excision with 0.5 cm margins. The possibility of a regressed melanoma was raised at our melanoma tumor board. The scar extended quite deeply and was very uniform, suggesting to me that there had been a prior surgical procedure at this site, despite the history of 'no known prior biopsy'.