Case Number : Case 2493 - 24 January 2020 Posted By: Dr. Richard Carr

Congenital nevus, with "ancient" changes.

Congenital nevus with proliferation nodule? if it is a longstanding lesion with no clinical atypical features, then the mitotic activity is mostly just a result of repeated trauma. 

Looks innocent! Hope so. But old age, epidermal consumption (? trauma), deep mitoses, ? maturation, can't see enough stroma inbetween the nevus cells. Before I go to Congenital nevus with proliferation nodule, I want to see P16, ki67, HMB45, MelanA? To exclude nevoid melanoma. 

I agree

it could be nevoid melanoma

also it is difficult to differentiate between atypical proliferation nodule or melanoma

IHC could be helpful

Suspicious of nevoid melanoma.

Ki67 is high, so it could be nevoid melanoma but still how to differentiate it from nevoid melanoma like pattern of proliferation nodule? Especially that the clinical is describing a long standing congenital lesion with no atypical features? Will molecular be of need/help here? Interesting case! 

Very interesting case. The blue population is atypical if compared with the residual congenital nevus in fig 7...but I hope never have to go trough this lesion during my routine work!!! 

Good discussion. Agree this is a challenge and therefore somewhat subjective. I reported it quite a while back (it was a referral). For me the density of the infiltrate, fairly obvious mitotic activity and high Ki67 proliferation, when comparing with the benign dermal naevus was enough to favour a diagnosis of dermal melanoma arising in a pre-existing benign naevus. Another feature which I don't associate with benign naevus is the presence of apoptotic bodies. I think this is also a clue to naevoid melanoma and not discussed in the textbooks.

Thanks Richard. 

. Dr Richard. I favor nevoid melanoma too . No maturation ki67 and paralel layout of cells. Thanks for sharing.