Case Number : Case 2697 - 06 November 2020 Posted By: Dr. Richard Carr

Keratoacanthoma like squamous cell carcinoma

Some follicular differentiation, infundibular-like and ORS/IRS-like...and an infiltrative growth pattern. So agree with SCC, but favor a fSCC.

Lesion was from the shoulder it that helps?

Well differentiated SCC with keratoacanthomatous features.

I'm waiting for the IHC to be posted - I'll nudge the team.

12 hours ago, Dr. Richard Carr said:

I'm waiting for the IHC to be posted - I'll nudge the team.

IHC posted

177 views and 3 brave soles - what is the world coming to?  Happy festival of lights. Let's hope we can bring a little more light into the world.

Okay I think we need a Karl Popper quote to encourage debate.....

When I speak of reason or rationalism, all I mean is the conviction that we can learn through criticism of our mistakes and errors, especially through criticism by others, and eventually also through self-criticism. A rationalist is simply someone for whom it is more important to learn than to be proved right; someone who is willing to learn from others — not by simply taking over another's opinions, but by gladly allowing others to criticize their ideas and by gladly criticizing the ideas of others. The emphasis here is on the idea of criticism or, to be more precise, critical discussion. The genuine rationalist does not think that they or anyone else is in possession of the truth; nor do they think that mere criticism as such helps us achieve new ideas. But they do think that, in the sphere of ideas, only critical discussion can help us sort the wheat from the chaff. They are well aware that acceptance or rejection of an idea is never a purely rational matter; but they think that only critical discussion can give us the maturity to see an idea from more and more sides and to make a correct judgement of it.

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So in the spirit of critical debate may I please may I ask for your diagnostic criteria? Or this case will be unsolved forever.

sir p16,p53 expression is in the basal layers. Ki 67 is seen in basal portion of tumour

If it is a SCC i would expect p53 in all the tumour cells and ki 67 high

p16 is cytoplasmic, p16 is also not a useful marker to distinguish between KA and SCC,

p53 expression is more basal 

overall could be keratoacanthoma sir

And if I'm here making a fool of myself on subjects I'm not an expert on, it's because I believe in what you have just tell, Richard.   So I would be happy if you would explain the special HC and IHC stain. 

We are all fools in this field I'm afraid - including me. Those that have made no sins should cast the first stone!.

The secret is to know you don't know. Ignorance is not the lack of knowledg . [typo intended!] But the the lack of desire to acquire it.

H&E features for me favouring a KA (rather than well differentiated SCC).

IHC: wild type p16 (strong mosaic, wild type p53 (moderate to strong in periphery but weakens in mid zone and no moderate or strong in the inner third), peripheral only Ki67 all c/w KA.

There are publications suggesting up to 90% null expression of p16 in SCC (Mortier et al 2002). Seems this was not picked up widely. I've found diagnostically ~90% of SCC have mutant IHC patterns for p16 (~80% null/cytoplasmic only) & p53. I'm doing an ongoing audit. Obviously if KA are SCC they should show a similar pattern but I've found typical KA have pattern seen above. 

Typical KA is a tumour suspected to be benign or low risk (one can never say never for metastasis of any purported benign appearing lesion) which should be distinguished from SCC to avoid over-treament of patients with perineural and venous invasion. The malignant potential of typical KA appears to be minimal but of course the diagnosis is highly challenging especially in partial / incomplete specimens. In my opinion patients should be discussed in a multi-disciplinary board if there is any concern about the diagnosis (which is nearly always the case except for near completely regressed lesions. I think highly challenging proliferative lesions on the central face with perineual or venous invasion would best be referred to an expert who is familiar with all the pitfalls (and there are few in the world - or practically zero who've never made mistakes hence the tendancy to overcall them).

Please e-mail me: richard.carr@swft.nhs.uk if you like to take the challenge of 15 digitised cases I'm currently circulating nationally & world wide (still about 4 days to go but we have around 100 responses so far). I'm sure we'll visit the topic again. 3 hours of talks & Q & A this Friday via Zoom open for international participation (if you've taken the challenge and submitted a response).

I'd like to collect KA with perineural and venous invasion or KA-like SCC that have metastasised or lesions called KA that metastasised - contact me at the same e-mail should you wish to share a case.

Warm regards

Richard 

Thank you very much, Richard. 

Apologies for short post today : I'm a bit frantic with the meeting and maybe one day I'll publish a monograph on KA.