Case Number : Case 1464 -03 February Posted By: Guest

The lesion seems to be quite extensive, both with nested and individual mélanocytes. Slight confluence of nests and focal extension to the adnexae. The neoplastic cells are moderately atypical with presence of small nucleoli. A conspicuous lichenoid lymphocytic infiltrate altogether with the clinical setting makes me favour melanoma in situ.

I see a lichenoid regression adiacent to malignant melanoma in situ and a  transition of malignant melanoma to lichenoid tissue reaction with loss of melanocytes at the dermal-epidermal junction in the lichenoid reaction. I favour a regressing early invasive melanoma

I agree that some of the criteria of regression are present but to my eyes the lesion is completely in situ. I would like to know how do the expert dermatopathologists diagnose lesions like this one, do you add a comment stating that areas of regression cannot be ruled out?

i'm a general pathologist, not at all an expert dermatipathologist, but i see a dermal scarring in first image. 

Atypical junctional melanocytic proliferation, with focal regression (dermal fibrosis, vascular proliferation and inflammation). Overall, in-situ malignant melanoma. Is this an incisional biopsy?

In a lesion like this in your usual practice do you stage it as a pTx or a pTis?. Based on the CAP we should stage it as pTx right? (and the surgeon and patient will hate us)

It looks like a shave biopsy.  I think you are right to consider the possibility of a lichenoid reaction to melanoma in situ but the location and predominant nesting suggest we should also consider a junctional dysplastic naevus.  The small focus of scarring could be secondary (e.g. to follicle rupture, previous non-diagnostic biopsy, treatments or local trauma etc. etc.  As an aside, in addition to the features mentioned by Nitin I like to see a break in the dermal component (not relevant here). I would examine multiple levels but assuming this is representative leave the diagnosis slightly open and advise complete excision with clear margins.

This was a tough case but we thought we could not exclude at least melanoma in situ with a lichenoid background.  The lichenoid nature of the lesion precluded estimation of true biological potential; therefore, early invasive melanoma could not be excluded. As this was a shave biopsy, we recommended complete excision with margins appropriate for melanoma in situ, and a caveat that the lesion may act in a more aggressive fashion than the typical MMIS. We would stage as at least pTis and clarify in the body of the report that the presence of dense inflammation complicates our ability to accurately determine depth.

Thank you Doctors for you useful comments. Great case