Case Number : Case 2054 - 20 April 2018 Posted By: Dr. Richard Carr

Definitely atypical but I still have the feeling that it's relatively circumscribed and the epidermal component is arranged predominantly in nests. The dermal melanocytes appear mature with descent. But the melanocytic lesion shows a certain degree of cytologic atypia although I would not call severe. There appears pagetoid spreading in the center.

Melanocytic lesions of the vulva are sometimes very difficult to classify because the vulva is a special site. I'm not convinced this is a melanoma. I would classify this lesion as atypical genital compound nevus. Would recommend conservative re-excision if the margins are involved.

Agree with Anh’s comment and conclusion. 

I think this is melanocytic lesion with atypia related to the topography. I agree with the proposed management, complete excision.

Agree with atypical site nevus

Worried about melanoma. There is asymmetry with single cell predominance and scatter on one side (figure 2). There is irregular pigmentation. Adnexal extension is present but this can be seen in genital nevi. 

Nevus of special site.

Well done Arif. Beware the melanoma of special site!  I did consider special site naevus also and even raised it with the clinical colleagues having seen what appeared to be relatively demarcated separate lesions on the vulva. However at MDM there was cause for concern and we felt definitive diagnosis could not be rendered on punch specimens. Fortunately all three lesions were excised in one quite large excision. The central lesion (thought clinically to be seborrhoeic keratosis) was amelanotic melanoma Breslow 1.8mm replete with numerous mitotic figures. The upper and lower lesions that look clinically circumscript were all connected by atypical lentiginous and pagetoid melanoma in situ and considered to be "naevoid" melanoma I radial growth phase. So... beware giving a diagnosis on punch biopsies in general and especially on high risk and difficult locations where melanocytic lesions are concerned. In hindsight the degree of pagetoid spread and lentiginous lateral growth here is too much of a lesion of someone in this age group. The atypical genital naevus tends to be seen in the young and Pagetoid spread relatively infrequent or limited in degree. In this case I nearly fell headlong into the triggered trap so I am sharing it in the hope that we can all learn from it. I would say that despite being quite an experienced histopathologist, who has collected many slides over the years, I only had 7 genital melanocytic lesions in my entire slide collection, several of which were melanotic macules or melanoses so I suppose one does not see so many cases from this location in routine reporting.

Thanks Richard for sharing this difficult case. 

case.

Thanks for this useful case-sharing. 

Thank u Dr Carr!