Case Number : Case 1805 - 28 April - Dr Richard A Carr Posted By: Guest

I am checking out the venue for the LDS tomorrow so have posted Dr Richard A Carr's Friday Spot Diagnosis Case a day early, enjoy.

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Geoff Cross - DermpathPRO Projects

Keratoacanthoma

SCC, verrucous/cuniculatum type.

I think of verrucous carcinoma.

Keratoacanthoma.

I thought of KA

SCC probably verrucous

KA

Keratoacanthoma vs well-differentiated SCC.

It does have the glassy enlarged keratinocytes, the architecture and eosinophils in the dermis to favour KA over SCC.

Also thought of KA for CPC

KA

I have posted an additional comment to my case from 2 weeks ago. Case 1795 14th April (I am happier with a diagnosis of subungual exostosis).

KA, second verrucous. Because of the glassy appearance and neutrophils I favor KA; though it doesn't show the typical cup architecture filled with keratin. 

I think this is a very challenging case but I favoured a well differentiated (follicular) squamous cell carcinoma. The architecture is somewhat difficult due to the nature of the specimen but the lesion lacks the central crater and the individual lobules are rather rounded and pushing rather than the more infiltrative pattern of a proliferative KA with prominent elastic and collagen entrapment (typical of KA) lacking in this lesion. A more established or maturing KA should have more evidence of regression, lichenoid perilesional inflammation and fibrosis, than we see here. I did ponder if there was background hidradenitis supurativa (some slightly comedonal follicles in the background) and given the young age. I also wondered if the lesion could be induced by HPV. I am awaiting follow-up. Prognosis should be excellent as the lesion is well differentiated and has almost entirely pushing borders.

On 4/29/2017 at 16:34, Dr. Richard Carr said:

I think this is a very challenging case but I favoured a well differentiated (follicular) squamous cell carcinoma. The architecture is somewhat difficult due to the nature of the specimen but the lesion lacks the central crater and the individual lobules are rather rounded and pushing rather than the more infiltrative pattern of a proliferative KA with prominent elastic and collagen entrapment (typical of KA) lacking in this lesion. A more established or maturing KA should have more evidence of regression, lichenoid perilesional inflammation and fibrosis, than we see here. I did ponder if there was background hidradenitis supurativa (some slightly comedonal follicles in the background) and given the young age. I also wondered if the lesion could be induced by HPV. I am awaiting follow-up. Prognosis should be excellent as the lesion is well differentiated and has almost entirely pushing borders.

Did you perform p16 and p53 Richard?

I don't think so. I did not make a note of having done so in my report. They tend to be less helpful in well differentiated lesions in my experience showing wild type staining or only slight up-regulation. I have not systematically studied lesions such as this though.

Follow-up now kindly received. The patient underwent a re-excision at one of our larger cancer centres in the UK and was reported as residual well differentiated squamous cell carcinoma, completely excised. Nothing mentioned about hidradenitis suppurativa.

I have to say I have re-commented on case 1282 (22nd May 2015) that I now favour that lesion also be a well differentiated SCC with some KA-like features (ano-genital lesion with background lichen sclerosus). Currently I will be very wary about making a diagnosis of KA on anogenital skin as I believe well differentiated skin cancers at this location can closely mimic the cytomorphology (abundant glassy pink cytoplasm) making distinction near impossible on small or partial specimens let alone complete excisions. Counter-intuitively proliferative KA in general look altogether more worrying (poorly differentiated at the periphery) lesions than these rather bland pushing tumours that are KA-like.