Case Number : Case 2511 - 20 February 2020 Posted By: Saleem Taibjee

granulomatous panniculitis

suggest PAS stain and examine under polarizer, something is there in the giant cells

Granulomatous panniculitis with esinophils. Bug stains (especially PAS and silver methenamine), tissue culture and verification of foreign body

Miescher radial granulomas...what about erythema nodosum?

There were no organisms seen on special stains, and no polarising material on polarising microscopy.

The clinician was especially querying erythema induratum.

Here is the subsequent dialogue which I had with Professor Luis Requena (the 'god of panniculitis') about this case:

"Dear Professor Requena

I would be very grateful for your expert opinion on a panniculitis case sent to me for second opinion by one of our local hospitals/pathologists.

The patient is a 76 year old man with lumps behind the right knee. The clinician is querying erythema induratum. I do not have clinical images.

After attending your superb lecture on panniculitis previously some years ago, my reasoning is that this is more likely to be erythema nodosum (a chronic scarring variant) in view of the predominant septal (vs lobular) involvement, and absence of a clear-cut vasculitis. The histology is quite granulomatous (which as I noted can be a feature of late stages of erythema nodosum), but I could not appreciate definite Miescher’s radial granulomas or granulation type changes at the septal:lobule interface, but I must admit that I find these signs quite difficult to fully appreciate. From your lecture you had indicated that erythema induratum is very much predominantly lobular, which I think is not the case here.

Many thanks indeed for your advice and thoughts."

Professor Requena's reply:

"Dear Dr. Taibjee:

I entirely agree with your interpretation and a late stage erythema nodosum in a granulomatous phase is the best possibility.

Best regards. Luis Requena, MD"

sir was it unilateral or bilateral

if bilateral  then EN if unilateral we need to think

unilateral. Yes, agree unusual for EN, but still possible.

Erythema nodosum