Female patient, 56 years old, with leukocytosis and lymphocytosis and Lymphoma suspicion - Peripheral blood sample with white blood count 23,200 cells / TCD8+ restriction (TCD4/TCD8 ratio 0.1:1). Panel, Immunophenotyping and Gating Strategy. Triage of all the samples was analyzed in the LST tube. The TCRCBeta 1 tube was designed based on EuroFlow’s Orientation Tube for Immunodeficiencies (PIDOT), using CD3, CD4, CD8 and CD45 as “backbones”, CD27 and CD45RA to discriminate T-cell subsets, CD16 and CD56 to exclude NK cells, and including TCRCBeta1 in the PE channel. Results: 59% T Cells: *52.5% TCD8+: 39.4% TD (terminally differentiated) phenotype with increased absolute levels (9,141 cells/μL - normal age range 8-500) CD7dim CD27(-) CD45RA-/+ TCRCBeta1+5% (monoclonal); 0.7% Naive CD45RA+ CD27+ TCRCBeta1+30% (polyclonal), 1.2% CM/TM (central/terminal memory) CD45RA(-) CD27+ TCRCBeta1+19% (polyclonal); 9.7% EM (effector memory) phenotype with increased absolute levels (2,250 cells/μL - normal age range 2-323) CD45RA(-) CD27+ TCRCBeta1+5% (monoclonal). *4.9% TCD4+ TCRCBeta1+44% (polyclonal). Immunophenotype: CD45++ CD3+ CD8+ CD38dim CD45RA-/+ CD45RO-/+ CD2+ CD5++ CD7+FR TCR ALPHA-BETA+ PERFORIN+ TCRCBETA1 ++5%; Negative expression: CD25 CD26 CD27 CD28 TCL1 CCR7 TCR GAMMA-DELTA CD11C CD30 CD16 CD56 CD94. Morphology: In the analyzed smear, 32% of atypical medium-sized lymphoid cells were observed, with a globose nucleus, generally eccentric, with poorly condensed chromatin with an outline of a nucleolus, and a moderately basophilic, polarized and granular cytoplasm. The inicial diagnostic hypothesis was T-Lymphoma, NOS (the authors judged that there were no sufficient NK antigens expressed to characterize T-LGL). However, further investigation showed the patient had no identifiable T Cell lymphoma, and she eventually was diagnosed with Thrombotic Thrombocytopenic Purpura, with classic symptoms and laboratory confirmation. Since the implementation of TRBC1 for detection of abnormal T-cells, persistent clonal expansion of large granular lymphocytes (T-cell clones of uncertain significance/ T-CUS) have been reported in a variety of clinical conditions, such as hematological neoplasms and autoimmunity. The incidence of T-CUS increases with age, and probably represents reactive T-cell small clones (so called immunoclones), with less than 20% of total lymphocytes or 400 cells/mm3, highly prevalent in patients without T-cell malignancy. Most reactive T-CUS cases are CD8+ or CD4+/CD8+ double-positive.