Case Number : Case 2877 - 16 July 2021 Posted By: Dr. Richard Carr

I'm inclined to think this is a recurrent/traumatised/sclerosed naevus (of special site). 

Special site Nevus, with some traumatic effect. 

This case was challenging but I favoured a special site naevus and advised watchful waiting. Nice symmetry, lack of pagetoid spread, good lateral demarcation, no significantly worrying features in the dermal component. p16 preserved mosaic and low Ki67 proliferation index. A highly respected UK colleague had favoured a melanoma in situ for the impressive junctional proliferation and I was sent the case for a further opinion. It's normal to get a range of different opinions on such cases but on balance I favoured it to be all benign / atypical special site naevus.

Dear sir,

 Atypical genital nevi are rare melanocytic lesions that most commonly arise on the vulva of young women. they behave in a benign manner. Here the lady is aged 70 years and we do not have information how long the lady had the nevus. so clinically melanoma is high on mind. with IHC we can conclude this. But this your years of wisdom. Now is it mandatory any atypical nevus or melanoma in doubt we have to do these markers, what is the role of PRAME here. Also, is there any age limit to consider nevus at special sites

please clarify Sir

18 hours ago, Krishnakumar subramanian said:

Dear sir,

 Atypical genital nevi are rare melanocytic lesions that most commonly arise on the vulva of young women. they behave in a benign manner. Here the lady is aged 70 years and we do not have information how long the lady had the nevus. so clinically melanoma is high on mind. with IHC we can conclude this. But this your years of wisdom. Now is it mandatory any atypical nevus or melanoma in doubt we have to do these markers, what is the role of PRAME here. Also, is there any age limit to consider nevus at special sites

please clarify Sir

 

I also have similar concerns as you for this case. at least it is dysplastic nevus if the junctional not reaching to the degree of melanoma in situ. the dyhesive nature of those melanocytes maybe duet to special site. but the relative florid growth is worrisome, I would do PRAME in this case, P16 only meaningful to me if there is complete loss in the melanocytes. melanoma can have intact preserved P16. 

Thank you for the additional discussions. PRAME could be helpful. I don't have it available locally but could have requested it to be sent away and waited for it. When assessing an IHC one has to have a feel for the prior probability and interpret the result in the light of this. My prior probability is relatively low but a positive PRAME could move the goal posts more into the uncertain end i.e. cannot rule out early  melanoma. The discussion then becomes what margins are acceptable for thin somewhat challenging uncertain lesions and I think we already have that problem. Watchful waiting (and I mean careful follow-up given the location with informed consent to the pros and cons) should remain a safe and viable option if the patient prefers (the location and lack of history cause problems for guiding management. I think we have to remember that harm can come from over-diagnosis and over-treatment and from under-diagnosis and under-treatment and that for thin and inherently subjective lesions there is no "zero harm" option.

Very interesting case, I thought  it was in situ SSM due to "Contiguous proliferation of uniformly (e.g. > 50%) moderately to severely atypical melanocytes
in an area ≥ 0.5 mm2" as WHO indicates, however atypia is somehow subjective. I am glad I don't have to sign this one.

Regarding PRAME stain I must say that we haven't had great results,so far, in our lab, however we are using alkaline phosphatase (Red) instead DAB.

Again thanks