CASUS PRO DIAGNOSIS:  
32 old yrs male with diagnosis "Burkitt lymphoma: spread in gastric wall and bone marrow" in 2007.  
IH 2007(stomach, original lab, pre-therapic): CD20+ TdT- CD10+ Bcl6+ Ki67 up to 100%. Threpine biopsy 2007: CD20+ small infiltrate of large cells in BM, but nothing left in recutt slides. Serous degeneration, MDS like changes (seems to be after chemo changes).  
In 2008 february, after chemotherapy with anti-CD20 some scars and infiltration of the tumor is seen (gastroscopy). Biopsy was taken. Threpine biopsy (2008) was repeated (reactive changes). Blood, bone marrow without changes. LDH 660.  
IH 2008(stomach, our lab): CD20- (after immunotherapy), CD79a+, CD10+, Bcl6-, Bcl2+ (5%+), Mum1-(single dim +), Ki67 up to 100% and (SIC!!!) TdT+ 30% (stained twice for control), MPO/CD34/CD117-, CD43+, IgM-.  
IH 2007 (stomach, primary, restained in our lab now): CD10+ CD20+ Bcl6+ TdT- Ki67 up to 100% CD34/CD117- CD79a+ Bcl2- CD43+ IgM+.  
BOTH HISTOLOGY: Starry sky pattern, high proliferative activity, but prominent single nucleoli, some irregularities/cleaves of nuclei (esp. well seen in cytoplasmic stains: "lymphoblastic alike" morphology). Primary population maybe more monomorphic.  
 
QUESTIONS: 1. Final diagnosis: DLBCL Burkitt like ("atypical Burkitt lymphoma") with recidive tumor?. 2. Explanation of TdT+ gain and Bcl6, IgM loose in the Burkitt like lymphoma after treatment: B lymhoblastic transformation? Oth.? 3. The reasons of TdT+ (technical? Oth.?)  
 
QUOTATION: "TdT is NEVER expressed in other NHL except LBL..."  
 
Thank you for the comments.