Case Number : Case 2022 - 06 March 2018 Posted By: Uma Sundram

Squarish outline of the biopsy suggests fibrosis in the dermis. Dermis shows thickened collagen bundles and granulomatous infiltrate arranged in tiers. Infiltrate has epithelioid cells and Langhan's giant cells. The CPC leads to necrobiosis lipoidica.

given the presence of histiocytoid cells around nerves, wondering if this could be single lesion leprosy

Thanks Dr Urmila for pointing out the granuloma around the nerve and raising the possibility of leprosy. Having worked in a 300-bed leprosy hospital for several years, leprosy is a topic very close to my heart. But the gross changes in collagen and vessels as well as the involvement of the panniculus rule out leprosy. In fact, nerve damage is a feature of necrobiosis lipoidica and some lesions actually have a sensory loss.

Agree with above comments...but my impression is of some septal pattern of ingjury. We don’t see subcutaneous tissue so my question is: why not an erythema nodosum?  

It is a yellowish plaque, thats why necrobiosis lipoidica. EN presents as a tender erythematous nodule.

You have me convinced Anil. Granulomatous variation of NL was my first and practically only thought.

Thank you everyone. Anil is spot on! NL was also my first and only thought. The clinician didn't know what this was (!) and was worried about MTB. The referring pathologist was worried about leprosy. I did also consider EN, but given the amount of dermal involvement, this was lower on my differential. I concede that not much panniculus is present to completely exclude EN; but the clinical argued against it. I don't think I've seen cases of classic EN where even the superficial subcutis was not inflamed, so that argued against EN as well.

Nice case, thanks for the great discussion

Thanks Uma!!! Great case.

Good case and very nice discussion ! 

I also agree with Necrobiosis Lipoidica .

just would like to do one Fite stain as there is perineural granulomatous infiltrate ! 

Great case. NL was my thought too!