It seems to me that the following findings are present: follicular hyperplasia, monocytoid B cell hyperplasia, and packets of epithelioid histiocytes. The latter are found in the interfollicular space and seem to surround a focus of progressive transformation of germinal centers. These are the main criteria for toxoplasmosis. I am not sure what to make of the EBV+ cells; possibly they are due to an earlier EBV infection. The possibility of toxo can be investigated serologically. It may be worthwhile to know if the patient has had exposure to cats or kittens.

Please refresh your web page- next photos are loaded. Thank you.

I've not Ki67 and EMA (pending) for a moment.

Thank you for preliminary comments. I will append add photos and stains on demand.

Despite atypical RS and Ho like cells in clusters, monocytoid B CD20+Bcl2- population ("immature histiocytosis") in sinuses seems to me a little too cleaved and too polymorphous.

your working hypothesis would also reflect my working hypothesis, particularly facing the CD30 and Cd15 co-expression as well as presence of LMP1 in the HRS-cells. i would suggest to extend the pannel for Hodgkin lymphoma by CD45RA (should be negative), PAX-5 (should be dim+ or negative), EBNA-2 (should be negative) and (optinally) e.g. p53, cyclin D1, D3 or E (positive in the majority of HRSC). but I think that the clinical history, the morphology and the phenotype (CD15!) are primarily in support of perifollicular Hodgkin lymphoma.

Thanks. LCA and p53 and PAX are ok. Another items- out of my possibilities:)

CD79a could help, too.  
 
Was there toxoplasmosis serologically, after all?

I do not check info about serology, but- just get archival materials with... more prominent "immunoblastic" lymphadenopathy and giant cells similar to demonstrated above.. I will request IH on these cases. The problem was CD30+ large cells without definite CD15+ reaction. In some tonsilar material too...

You would almost always get reactive CD30+CD15- large cells in toxoplasmosis lymphadenitis in a younger person. Your patient is almost 80, I really have no experience with such cases.

... CD15+...

Are all large cells negative for B-cell markers? the alternative diagnosis could be the EBV-related lymphoproliferative disorder in the elderly (see attached). Can be sometimes very difficult to differentiate from Hodgkin lymphoma.

Sorry for the delayed comment. I, as well do favor interfollicular HL, EBV+. Some images show morphologically typical RS cells, CD30+,CD15+. I would like to see on a high power image if atypical cells do express CD20. Thanks Anja for mentioning EBV-related lymphoproliferations in the elderly, thanks also for the reference. I have seen a number of such cases, which are very difficult to differentiate from HL. However, in all the cases I have seen atypical cells were CD20+, CD30+, but there were no CD15+ cells.  
Without any information about Toxoplasma serology we cannot tell if the epitheloid cell nodules are an expression of toxoplasmosis or a nonspecific reaction to the tumor.

Please find some add stains. Thank you for pdf and comments.

Thanks, Ugnius, the added stains(PAX5+,p53+ and cyclin D1+) are a further support for our diagnosis.

Sorry for the late reply. I completely agree with Dr.Hurwitz that this represents classical Hodgkin lymphoma, interfollicular variant. It cannot be ignored that you have perfect morhologic and immunohistochemical phenotype for this diagnosis. I do not agree that Hodgkin-like fits here, because even if this represents minor or minimal evidence of cHL and association with Toxo-type pattern of lymphadenopathy, it cannot be ignored as it is not ignored when associated with CLL or other lymphoproliferative disorders including even T-cell lymphomas. From the evidence that I can identify on the images, I would like to see Toxo serology, but I would not ignore cHL, whatever results show.

All, histopathology and immunophenotype support the diagnosis of interfollicular Hodgkin lymphoma, p53 and Cyclin D1 are also in agreement, so that there is enough evidence to diagnose Hodgkin lymphoma, which was also my firt impression.