Bone marrow trephines from T-LGL leukemia patients showed interstitial clusters and intrasinusoidal linear infiltrations of CD3+/CD8+/CD57+/granzyme B+ lymphocytes, reactive lymphoid nodules, and decreased or normal granulocyte precursor count with left-shifted maturation. The gene discussed is B3GAT1; the disease is T-cell large granular lymphocyte leukemia.