very difficult case, I would not straightly forward diagnose DLBCL, particularly since the lesion is not destructive. an "exploading" germinal center could be similar. I would stain the critical cells for CD10, bcl-6, bcl-2, CD138, MUM1, CD79a and CD30 in order look if they have a germinal center phenotype or phenotypic characteristics of extrafollicular blasts. in the setting of infection, I would carefully interprete light chain restriction. IgH PCR could bring some clarity if polyclonal.  
 
the presence of megas as well as the sharp demerkation of the lesion are further points in favor of a benign process.

Given the histology and PCR result, it is hard not to call this B cell lymphoma, but I think if it were my case, I would not do that. I would call it an atypical lymphoid infiltrate with a comment that the focus is limited and the clinical significance of the lesion is not clear. This would account for the possibility of a small indolent B cell clone, and doesn't rule out malignant lymphoma. The more we look for clones, the more we find these small clonal populations of unknown significance. It is not clear to me that the lesion is entirely excised; if not, it should be, with a dilation and curettage if not previously done. The patient should probably undergo some non-invasive staging, e.g. MRI, and if absolutely nothing more is found, then I think it would be safe to watch her closely for the next year or two. Your other cases are interesting. It would be great if you could tie these to some organism or other etiology.

PCR IgH result was unsatisfactory: nor clonal, nor polyclonal signal was generated (sorry for terminology, I'm not a performer, only believer).

I would be very reluctant to call this lesion lymphoma. You mentioned Chlamydia infection. Chlamydia is a well known cause of plasma cell endometritis, lymphoid follicles and nodules of transformed lymphocytes have been described in some cases. Wait and watch after a minimal staging seems a good approach in this case.

On the morphologic basis alone, this is at least an atypical lymphoid proliferation. However, we would not rule out normal or benign GC cells by using Bcl-2 or CD10, because of course Burkitt will have the same immunophenotype as normal GC cells. As there are numerous apoptotic and mitotic figures, the immunophenotype, extranodal location, and the medium size of cells, and the patient is young, I am afraid that we cannot exclude a partial involvement by Burkitt lymphoma. Because of that possibility, more aggressive approach to staging and imaging may be needed.  
I do not have much experience with Chlamidial endometritis, but thought that the transformed cells in this disorder are centroblasts in normal germinal centers. Please correct me if this is wrong. Also, we unfortunately do not have any follicular dendritic cell markers to see if they are present or not. I am not sure if there is any benign disorder outside of the germinal centers with sheets of Bcl-6+ cells that have Ki-67 ratio of about 100%.

Thank you. Really material is exhausted. Oth stains are unavailable. We are waiting the patient ariving to hemato center.

morphology, phenotype and genetics are highly suspicous for an aggressive b-cell lymphoma (dlbcl or bl). fish would be another option.