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 lymp Show more
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
Composite lymphoma, defined as two or more distinct well-defined entities involving the same anatomic site, is rare. Here we report a 79-year-old woman with composite mantle cell lymphoma (MCL) and ly Show more
Composite lymphoma, defined as two or more distinct well-defined entities involving the same anatomic site, is rare. Here we report a 79-year-old woman with composite mantle cell lymphoma (MCL) and lymphoplasmacytic lymphoma (LPL) involving bone marrow at the time of initial diagnosis. The patient presented with splenomegaly and lymphadenopathy and laboratory studies showed an elevated serum IgM level and IgM kappa paraprotein. Bone marrow evaluation showed concurrent involvement by MCL and LPL, supported by immunophenotypic studies that revealed two distinct aberrant B-cell populations. Next-generation sequencing analysis identified concurrent MYD88 and CXCR4 mutations and fluorescence in-situ hybridization showed CCND1 translocation, supporting the diagnosis of concomitant MCL and LPL. In conclusion, composite lymphoma can present in the bone marrow. The use of ancillary studies was essential in reaching the diagnosis in this case, as the results excluded the possibility of MCL lymphoma with plasmacytic differentiation, as well as other CD5- and CD10-negative small B-cell lymphomas. Show less