Case Number : Case 2684 - 20 October 2020 Posted By: Uma Sundram

Another top-heavy histology.  This is a small lesion with full-thickness epidermal necrosis and adherent crust.  Not much underlying inflammation making ecthyma unlikely. 

I think this is a lesion with exogenous cause - dermatitis artefacta, or some form of thermal or chemical injury.

See below. 

A perforating dermatitis with trans epidermal elimination of cellular debris containing collagen vertical fibers. I don’t  know if it is Acquired Collagenosis Perforance or some other similar pathology ( dyabethic? Renal failure? traumatism? ) Waiting for the answer. 
 

Agree with Vincenzo, it looks like a biopsy that was taken from a relatively late/old lesion of a perforating dermatoses showing mostly trans-epidermal component in the available sections. Further levels/stains may shed more light on what is eliminated and any dermal component/connection.

Agree with perforating dermatosis- transepidermal elimination of collagen fibers is evident. 

Acquired perforating disorder. The patient has chronic renal failure and is on dialysis.

Lovely!