Case Number : Case 3052 - 18 March 2022 Posted By: Dr. Richard Carr

It's an infiltrative tumour of spindle cells with a hint of vasoformation and pigment which could be melanin or hemosiderin (taking into account the extravasated erythrocytes). Angiosarcoma and melanoma are the two top differentials. Immunos will be needed to arrive at the diagnosis.

Favor AFX because of: 1-pigmented atypical multinucleated cells seems xantomatous/histiocytoid; 2-the epidermal basal focal atypical hyperplasia is keratocytic committed, not melanocytic, in keeping with AK, not with lentigo maligna. 

SLAM differential, needs IHC.

This is the xanthomatous variant of AFX with a lot of foam cells. Not that cellular or mitotic but p53 is stronly positive and highlights the lesion. p16 is null (>90% of cases I've tested are null). CD10 was diffusely positive. Other markers epithelial, melanocytic & vascular negative. I now do p53, p16 and Ki67 routinely for the lower cellularity and more mildly pleomorphic variants of AFX. p53 can be high or null. 

On 23/03/2022 at 14:58, Dr. Richard Carr said:

This is the xanthomatous variant of AFX with a lot of foam cells. Not that cellular or mitotic but p53 is stronly positive and highlights the lesion. p16 is null (>90% of cases I've tested are null). CD10 was diffusely positive. Other markers epithelial, melanocytic & vascular negative. I now do p53, p16 and Ki67 routinely for the lower cellularity and more mildly pleomorphic variants of AFX. p53 can be high or null. 

Have you ruled out melanoma with s100 or only by morphology? I think p53 can be pretty high on desmoplastic melanomas too. Great case with great photos!

Yes S100 negative. I wouldn't routinely add other melanocytic markers unless I was quite suspicious for melanoma as S100 is ~99% sensitive for melanoma.

My panel for a bog standard AFX is: CD10, S100, pan-keratin cocktails, p63. I've routinely been adding Ki67, p53 & p16 for the more indolent subtypes. I'll only add other differentiations specific markers e.g. vascular etc. if the case has some features suggestive. The treatment of all the differentials is excision with clear margins so in a resource poor setting arguable it's mainly academic as most lower grade, AFX-like spindle cell SCC and melanoma won't metastasise in any case.