Case Number : Case 838 - 3rd September Posted By: Guest

Large cell acanthoma.

Large cell acanthoma

Agree. Large cell acanthoma.

I shall give her the benefit of doubt.Malignant melanoma insitu.

I shall give her the benefit of doubt.Malignant melanoma insitu.

agree with large cell acanthoma.
image labelled as 'transition zone' is instructive!

Large cell acanthoma. A circumscribed area of epidermis with enlarged keratinocytes topped by hyperorthokeratosis. Like Dr. Bakshi, I found the transition zone very instructive.

Large cell acanthoma.

- Large cell acanthoma (pigmented variant).

[size=4] Nuclear and cytoplasmic enlargement of keratinocytes (maintaining similar nuclear/cytoplasmic ratio as normal keratinocytes), hypergranulosis, and hyperorthokeratosis.
Seeing a clonal proliferation of enlarged keratinocytes--well-demarcated against normal, smaller keratinocytes, as seen in the 'transition zone' photo above--with involvement of the basal keratinocytes, is helpful in differentiating it from simple reactive keratinocytes, which may result from chronic inflammation and/or irritation. When there is actinic dysplasia, the differential would then include actinic keratosis.
[MelanA and Ki67 stains show expected basal melanocytes, which are dwarfed by the surrounding enlarged keratinocytes, and absence of high-level scatter or high-level proliferative activity].[/size]

Agree with the "academic" diagnosis but the distinction seems to be rather academic from a relatively flat solar lentigo which, afterall, is probably just a thin seborrhoeic keratosis! For the clinicians (even most dermatologists are not over familiar with this diagnostic splitting) I like not to confuse them with some of our more "academic" diagnoses so I might label it "solar lentigo / thin seborrhoeic keratosis (so-called large cell acanthoma variant)".