Case Number : Case 3020 - 2 February 2022 Posted By: Saleem Taibjee

Amazing Desmoplastic Trichilemmoma. Intriguing features of IFK ( I remember when A.B. Ackerman said SK was a member of Trichilemmoma family ). 

1 minute ago, vincenzo said:

Amazing Desmoplastic Trichilemmoma. Intriguing features of IFK ( I remember when A.B. Ackerman said SK was a member of Trichilemmoma family ). 

Agree. Desmoplastic trichilemmoma in one of the tumors and ordinaty trichilemmoma in the 2 others. Multiple lesions make us think about genodermatosis. The patient is a bit older for this, but PTEN IHQ could be done for Cowden´s syndrome.

Agree with desmoplastic trichilemmoma

Agree with desmoplastic trichilemmoma

Yes, you have all correctly identified trichilemmoma, with desmoplastic component. This desmoplastic area is evident in the largest of the 3 fragments.

However, I was quite surprised by this case, because I had thought the 2 smaller fragments (images 5-10 above) had more of an irritated seborrhoeic keratosis/inverted follicular keratosis pattern based on the H&E, with lovely squamous eddies. I really learnt something from this case, now realising that squamous eddies can be seen in any irritated squamoproliferative lesion, and certainly not specific for sebk/IFK.

The CD34 stain below shows significant tumour staining in all 3 fragments, and hence all 3 lesions are trichilemmomas. Clearly Igor was confident of this on the H&E, but I needed the CD34 to help me along!

Of course, as a knee-jerk, we should mention the outside possibility of Cowden syndrome when reporting trichilemmoma, but I am yet to see a case of solitary trichilemmoma leading on to a diagnosis of Cowden. In this case, with multiple lesions, this becomes a more worthy consideration.

Seeing Igor's comments, I have managed to obtain IHC for PTEN this week from an outside lab, and this is also shown below. I have no experience of using or interpreting this stain. But I'm quite excited...I think that there is preserved nuclear expression of PTEN within stromal cells serving as a positive internal control, contrasting with loss/diminished nuclear expression within the tumour epithelium in all 3 lesions. What do you all think?... Of course, PTEN might be lost in sporadic tumours, but even so, now Cowden's really does need to be considered.

Thanks for the helpful and interesting dialogue on this case.

BW, Saleem

Difficult to interpret, because it seems more dim than loss; but totally agree with a pathologically changed pten, if compared with positive internal control. Very interesting, Saleem. Thanks. And thanks to Igor, also.