Case Number : Case 2312 - 26 April 2019 Posted By: Dr. Richard Carr

Well, I do not know exactly how to give a name for this, but it seems to be a trichilemoma associated with a proliferating trichilemal tumor in the dermis. In the last figure on the right edge, we can see some follicular germ formation, so maybe this is all part of a small nevus sebaceus of jadassohn.

Very difficult for me. As Igor said, there is something trichilemmoma-like and something germ-like ( ?matrichal ) and inner root sheath differentiation also....PANFOLLICULOMA???

Central keratin filled crater with bulbous lobules emanating from it. I think that it's a pilar sheath acanthoma

I agree with Pilar sheath acanthoma

Yes. I was wrong. PSA is a better option. But...I was also thinking about a extrascalp proliferating trichilemmal cyst. 

I think this is a pilar sheet acanthoma. There is ditated infundibulum with broad acanthotic epithelial projections. Thanks for sharing.

pilar sheath acanthoma

My first thought was pilar sheath acanthoma too

My first thought was also pilar sheath acanthoma (having the infundibular component superficially and outer root sheath component in the deeper aspect) but based on the additional presence of the follicular bulbs and papillary mesenchymal bodies I settled on panfolliculoma. Although we are not seeing matrical or typical inner root sheath differentiation here. Of course there is an overlap with trichoblastoma that also shows papillary mesenchymal bodies and hair germinative differentiation and occasionally also inner root sheath and matrical differentiation and frequently infundibular-cystic structures. I guess it's a little academic as it's benign in either case. Pilar sheath acanthoma are one of the less common adnexal tumours but panfolliculoma for me is exceedingly rare and as I say I'm not sure it's worth separating it from trichoblastoma. I see PSA does get a spot in the 4th WHO Skin Classification but panfolliculoma (15 cases in the literature according to Kazakov's book) is not mentioned.