Case Number : Case 2869 - 06 July 2021 Posted By: Iskander H. Chaudhry

My first thought looking at the low-power pattern was that this was Jessner's lymphocytic infiltrate.  However, the cell population is rather too heterogeneous and includes quite a few plasmacytoid cells.  I wonder if this is blastic plasmacytoid dendritic cell neoplasm.

?PC CD4+ SM T-cell LPD vs PCMZL depending on further IHC/clonality studies. It is alway useful to consider syphilis serology in such cases as it is a great mimicker though the site is unusual especially if solitary lesion. 

Pseudolymphoma vs Marginal zone lymphoma top my list for further immunohistochemical studies..

granulomatous inflammation with dense lymphoplasmacytic cells with eosinophils

Any stains for infections such as PAS and GMS needed

I would also consider granulomatous slack skin.

Dr Chaudhry Diagnosis:

Special stains were all negative and this was not really concerned by the clinician.

As the biopsy was to determine whether it was a Lymphoma or pseudo-lymphoma, based upon the morphology and immunohistochemistry I have come to the conclusion that the features are those of pseudo-lymphoma which requires clinical correlation. 

After speaking to the clinician, it was brought to light that there was a history of insect bite and we queried whether it could be an insect bite reaction.

K/Lambda? Enough plasma cells in 6st picture. I’m not thinking about GSS-like MF because of the odd site(mid back); and not about BPDCN, because the BPDCN is a double negative ( CD3-/CD20-) and CD4+ neoplasm.  And morphologically this a small cell infiltrate, with some plasma cells and some monocytoid clear cell lymphocyte. Pseudolymphoma versus PCMZL. I don’t understand the last EmEo picture...it seems another case ( sarcoidosis? )

That is a great observation Vincenzo. Always consider a specimen mix-up when things don't add up!!

Kappa and lambda should confirm reactive cutaneous lymphoid hyperplasia and I often limit my markers in suspected lymphocytoma cutis, especially if the history is short. 

Without history inflammatory morphoea would be a consideration.

18 hours ago, vincenzo said:

K/Lambda? Enough plasma cells in 6st picture. I’m not thinking about GSS-like MF because of the odd site(mid back); and not about BPDCN, because the BPDCN is a double negative ( CD3-/CD20-) and CD4+ neoplasm.  And morphologically this a small cell infiltrate, with some plasma cells and some monocytoid clear cell lymphocyte. Pseudolymphoma versus PCMZL. I don’t understand the last EmEo picture...it seems another case ( sarcoidosis? )

I agree with the image that looks like sarcoid, made me confused as well

Apologies for the image (Sarcoidosis). That was an error and belongs to another case, wrong image have been deleted.

Really appreciates you for highlighting this issue. Thank you!

the histomorphology and IHCs pattern fit perfect with T cell rich pseudolymphoma, which I find could be quite difficult to differentiate from CD4+SMLPD. but the latter rarely have germinal centers. so more pseudolymphoma to me.