Indolent T-Lymphoblastic Proliferation (iT-LBP): A Review of Clinical and Pathologic Features and Distinction from Malignant T-Lymphoblastic LymphomaOhgami, Robert S. MD, PhD; Arber, Daniel A. MD; Zehnder, James L. MD; Natkunam, Yasodha MD, PhD; Warnke, Roger A. MDAdvances in Anatomic Pathology: May 2013 - Volume 20 - Issue 3 - p 137–140 doi: 10.1097/PAP.0b013e31828d17ec Review Articles Abstract Author Information In recent years, a new pathologic entity has emerged: indolent T-lymphoblastic proliferation (iT-LBP). iT-LBPs share immunophenotypic similarities with T-lymphoblastic lymphoma; however, T-lymphoblastic proliferations are clinically indolent, and unlike the malignant counterpart, these expansions of nonclonal terminal deoxynucleotidyl transferase (TdT)+ T cells do not require treatment. Here we review the clinical and pathologic features, which are required for an accurate diagnosis of an iT-LBP. We demonstrate specific criteria can be used to accurately diagnose iT-LBP, notably: (1) confluent groups of TdT+ T cells in a biopsy specimen, (2) relative preservation of surrounding normal lymphoid architecture, (3) TdT+ T cells without morphologic atypia, (4) absence of thymic epithelium, (5) nonclonal TdT+ T cells, (6) immunophenotype of developmentally normal immature thymic T cells, and (7) clinical evidence of indolence (follow-up >6 mo without progression). Department of Pathology, Stanford University Medical Center, Stanford, CA 94305 The authors have no funding or conflicts of interest to disclose. Reprints: Robert S. Ohgami, MD, PhD, Department of Pathology, 300 Pasteur Drive, Stanford CA 94305 (e-mail: firstname.lastname@example.org). © 2013 Lippincott Williams & Wilkins, Inc.