👤 Sanam Loghavi

In this study, we used optical genome mapping (OGM), conventional karyotyping, and next-generation sequencing to analyze cytogenomic alterations in 91 cases of T-cell acute lymphoblastic leukemia/lymphoma (T-ALL). Whereas karyotyping detected abnormal karyotypes in 55% of cases, OGM identified cytogenetic abnormalities in 97.8% of the cases and provided clinically relevant information beyond karyotyping in ∼70% of cases. OGM detected gene rearrangements in 80% of cases, including 24 recurrent gene fusions and 21 previously unreported putative gene fusions in T-ALL. Copy number variants were detected in 93% of cases, with interstitial deletions the most common. Gene mutations were detected in 93% of cases, with NOTCH1 being most frequent (in 57% of cases). Combining all data, most T-ALL cases harbored 3 or more cytogenomic aberrations. Specific cytogenomic alterations differed among T-ALL subtypes as follows: rearrangements of BCL11B and PICALM::MLLT10, deletions of 7p, and mutations involving DNMT3A, WT1, TET2, IDH2, and FLT3 were common in early T-precursor and near-early T-precursor subtypes. Rearrangements of TLX1, KMT2A, STIL::TAL1, and NUP214::ABL1, deletions of 9p, and FBXW7 mutations were frequently associated with the cortical subtype. We conclude that integration of OGM and next-generation sequencing with karyotyping enables comprehensive cytogenomic profiling of T-ALL that improves detection of clinically relevant genomic alterations and may inform disease classification and future studies of risk stratification. Show less

In acute lymphoblastic leukaemia (ALL), cytoplasmic CD3 (cCD3) is a defining marker for T-lineage, and CD19 plus additional B-cell marker(s) for B-lineage. We identified 23 ALL cases in which the lymphoblasts expressed both cCD3 and CD19, making lineage assignment challenging. These cases represented approximately 10% of cCD3+ ALL and expressed a median of two additional B-cell markers other than CD19, including CD79a (76%), CD22 (22%), PAX5 (57%) and CD10 (44%). Two cases were mixed for T/B-lineage ALL, both positive for BCR::ABL1 rearrangement. In the remaining 21 cases, IgH and/or IgK/L rearrangement were detected in 1 of 19 cases and TRG/TRB in 13 of 21 (62%) cases. Other T-ALL characteristic genetic abnormalities included NOTCH1 mutations (7/21, 33%), PHF6 (6/21, 29%), JAK3 (4/21, 19%), PICALM::MLLT10, TLX3::BCL11B, TRB::HOXA13, SPTAN1::NUP214 and deletion of CDKN2A/CDKN2B. In the 16 cases that demonstrated a T-ALL genetic profile, CD22 (2/16, 13%) was found to be a more specific additional B-lineage marker than CD79a (11/15, 73%), PAX5 (8/14, 57%) or CD10 (7/16, 44%). Our data suggest that mixed T/B-ALL is extremely rare, with most cases associated with BCR::ABL1 and blast crisis of myeloproliferative neoplasms. The majority of cases represent early T-precursor lymphoblastic leukaemia expressing aberrant B-cell markers. We also showed persistent CD19 expression in relapsed/residual disease (16/17, 94%), suggesting its potential role as a therapeutic target and as a marker for detection of residual/relapse disease in these ALL cases. Show less