LIM domain only 2 (LMO2) expression distinguishes T-lymphoblastic leukemia/lymphoma from indolent T-lymphoblastic proliferations.
AIMS
An indolent T-lymphoblastic proliferation (iT-LBP) is a benign, reactive expansion of immature terminal deoxynucleotidyl transferase (TdT)-positive T cells found in extrathymic tissues. iT-LBP can be challenging to distinguish from malignant processes, specifically T-lymphoblastic lymphoma (T-LBL), given the overlapping clinical and histological features. Recently, it has been shown that LIM domain only 2 (LMO2) is overexpressed in T-LBL but not in reactive immature TdT+ T cells in the thymus. On the basis of these findings, the aim of this study was to investigate the expression of LMO2 by using immunohistochemistry and its role in differentiating iT-LBPs from T-LBLs.


METHODS AND RESULTS
We retrospectively identified cases of iT-LBP and T-LBL from the pathology archives of four institutions. Seven iT-LBP cases (including five new cases that have not been reported in the literature) and 13 T-LBL cases were analysed. Clinical, morphological, immunophenotypic and molecular data were analysed. Immunohistochemical staining with LMO2 was performed on all iT-LBP and T-LBL cases. A review of five new iT-LBP cases showed similar morphological, immunophenotypic and molecular features to those of previously reported cases. All iT-LBP cases were negative for LMO2 (0/7), whereas 92% of T-LBL cases (12/13) expressed LMO2; the sensitivity was 92% (confidence interval 64-100%) and the specificity was 100% (confidence interval 59-100%).


CONCLUSION
We confirm previously published findings that iT-LBP cases show highly overlapping morphological and immunophenotypic features with T-LBL. Importantly, LMO2 expression is a sensitive and specific marker with which to rule out iT-LBP.
['Brar|Nivaz|N|', 'Butzmann|Alexandra|A|', 'Kumar|Jyoti|J|', 'Peerani|Raheem|R|', 'Morgan|Elizabeth A|EA|https://orcid.org/0000-0001-5880-9337', 'Grigoriadis|George|G|', 'Kumar|Beena|B|', 'Tatarczuch|R Maciej|RM|', 'Warnke|Roger A|RA|', 'Ohgami|Robert S|RS|https://orcid.org/0000-0003-1881-3440']
D000328:Adult D000368:Aged D003937:Diagnosis, Differential D005260:Female D006801:Humans D006965:Hyperplasia D007150:Immunohistochemistry D060588:LIM Domain Proteins D016399:Lymphoma, T-Cell D008232:Lymphoproliferative Disorders D008297:Male D008875:Middle Aged D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma D012189:Retrospective Studies
LMO2 indolent T-lymphoblastic proliferation T-lymphoblastic lymphoma