Case Number : Case 1645 - 14 October Posted By: Guest

Rounding off the week with a cracking case from Dr Richard A Carr, more to be posted at 6pm 

Cheers, Geoff

Follicular SCC

Agree, follicular SCC. Nice mucin? The scar is secondary to a previous excision of? Kobnerisation?

I was thinking more along the lines of inverted follicular keratosis, which can also show epithelial mucin.

There is prominent basal cell proliferation and increased mitoses would be expected in such areas. Not convinced that there is significant atypia for follicular scc.

1 hour ago, arti bakshi said:

I was thinking more along the lines of inverted follicular keratosis, which can also show epithelial mucin.

There is prominent basal cell proliferation and increased mitoses would be expected in such areas. Not convinced that there is significant atypia for follicular scc.

Agree it was the impression i had too. Irritated sebk with mucin and a pseudoglandular morphology. Last picture showing abrupt transition from basaloid and mature keratinocytes is quite suggestive

Arti and Raul are right as regards the lack of significant atypia. The clinical is worrisome though. Eroded plaque on a long standing scar. Mildly pleomorphic fSCC can be very difficult to differentiate from IFK. I thibk P53 will help. 

Me too agree with IFK.

The pattern of the immunos is that of a benign lesion so the diagnosis of sebk stands

Yes, agreed

immunos benign.

IFK although very unusual clinically ..

Agree with IFK. IHC definitely benign. Did think about it, but favoured a FSCC.

I agree with IFK, but something doesn't fit perfectly: the basaloid component looks like intraepidermal poroma/hydroacanthoma simplex..(.this recalls the reasonings about the eccrine nature of SK). However for diagnostic purpose I agree with above.

I had to eat humble pie on this case as I was ready to sign it out as a basaloid bowen's/SCC in situ when I was held back by a visiting dermpath trainee from the Netherlands.  Why is this not irritated seborrhoeic keratosis?  My low power spot diagnosis (basaloid, acantholytic, miotitic) had to be challenged and on further scrutiny - no atypical mitotic figures, relative uniformity of cells. So IHC requested that supported a diagnosis of irritated seborrhoeic keratosis / IFK.  I agree the history is concerning and I commented in the report that I have seen such mitotically active / clonal cases develop frank dysplasia. I currently believe seborrhoeic keratosis / IFK are infundibular keratoses (i.e. follicular tumours) hence can be exceedingly close to follicular SCC in situ (note they don't occur on non-hair bearing skin). Well done Arti / Raul and in particular Kimberly Van Oord!

Re: Vincenzo's point.  I have seen clonal lesions that I called SEBK develop over time in to porocarcinomas (at least two cases) so perhaps there is more to it than my first comment but we have to remember SEBK are very common lesions and perhaps are the innocent bystander and subtle clonal bowen's (epithelioma of Borst Jadhassohn) are very close to malignant hidroacanthoma morphologically.