I would suggest to perform kappa, lambda, EMA, and CD138 in the lymph node. The cells have plasmacytic appearance; the morphology is bland, not consistent with a blastic lymphoma. the BM morphology is not optimal.

Dear dr. Franco, your requested photos are in. The infiltrate is CD138-.

Hello, I looked at the case after the e-mail from Nina and I think that this is an acute leukemia, probably AML M0 type involving the lymph node. Lack of CD79a and CD3 speaks against ALL. CD4 can be positive in undifferentiated AML's.

Thanks Ania reading your comment I think your diagnosis is most probably correct. In this context we should see some high power images of the MPO staining on the lymphnode, in the periphery there are MPO+ cells, we have to see their morphology, could they represent evidence of maturation?, residual hematopoiesis?  
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Dear dr.Ana, nice to hear from you after nice Krakow time. Thank you for opinion. It this case I was surprised that "blastic" proliferation can be so similar to "marginal" and "low grade" pictures in HE... Thanks all of you involved in this extraordinary case.