Molecular genetic data favoring a sequential clonal transformation of a large B cell lymphoma into an anaplastic large T cell lymphoma, ALK-negative

A large B cell lymphoma with monoclonal rearranged, sequentially identical TRG and near identical IGH genes twice relapsed as an anaplastic large T cell lymphoma, ALK-negative. While these IGH and TRG rearrangements were also detected in both relapsed lymphomas, near identical IGK rearrangement was present in the primary and the first relapse, though not in the second relapse, and identical TRB rearrangement was detected only in both relapses, not in the primary. Normal T lymphocytes were the only T cell component found in the primary lymphoma, thus excluding a possibility that the primary lymphoma was a classic composite B and T cell lymphoma. Our data, particularly, the presence of sequentially identical monoclonal TRG and near identical IGH rearrangement in the primary and both relapsed lymphomas, favor a gradual transformation of a B cell lymphoma into a T cell lymphoma. In our opinion, this previously not described phenomenon likely represents a composite lymphoma in statu nascendi.