Case Number : Case 2900 - 18 August 2021 Posted By: Saleem Taibjee

necrotic keratinocytes and pigment incontinence in dermis

could it be a drug rash

The low-power views suggest confluent and reticulated papillomatosis, with blunt-topped papillomatosis and a degree of epidermal invagination by orthokeratotic keratin.  However, at higher power there is pigmentary incontinence and a lot of amorphous bodies in the papillary dermis.  Therefore I think I would want to do amyloid stains, with amyloid being my preferred diagnosis.

I noticed the necrotic keratinocyte but there was only one that i could see, so the features above seem more pertinent.

agree sir, could be lichen amyloid

Amorphous hyaline material in the papillary dermis, favor amyloid.

Fav amyloid, mid back usually macular amyloid 

Amyloidosis

Hi. Yes well done, this is a recent case of macular (cutaneous) amyloid. As Volha mentions, this is the subtype of cutaneous amyloid typically seen on the back, and shows a characteristic rippled macular  pigmentation pattern clinically. It is another example of 'invisible' dermatosis (or easily missed pathology).

It is also worth noting that keratin stains are usually more helpful than traditional amyloid stains such as Congo red in such cases. I include the relevant stains below. Interestingly, the choice of keratin stain does seem to matter, some cases seem to stain better for one pankeratin (e.g. MNF116, AE1/AE3, 34BE12) than another. But I am yet to make a firm conclusion as to which is the best, and might suggest requesting a couple of IHC stains in such cases. For example, AE1/AE3 was rather weak in this case compared to MNF116 and 34BE12.

BW
Saleem