Evaluation of the Cytomorphology, Immunophenotype, and Molecular Genetics of Lymphoblastic Lymphoma/Leukemia in Serous Effusion.

[INTRODUCTION] This study aimed to elucidate the spectrum of clinical manifestations, cytomorphology, immunophenotype, and the molecular genetic features of lymphoblastic lymphoma/acute lymphoblastic leukemia (LBL/ALL) in the context of serous effusions (SE).

[METHODS] A retrospective analysis evaluated the cytomorphological features, immunophenotype, and the cyto-histological correlations of twenty-one LBL/ALL associated with SE. Concurrently, bone marrow (BM) aspiration samples were analyzed using an integrated approach, including flow cytometry, reverse transcription PCR (RT-PCR), next-generation sequencing (NGS), or whole transcriptome sequencing (WTS).

[RESULTS] Of the 21 cases of SE LBL/ALL, 16 cases were T-LBL/ALL and 5 cases were B-LBL/ALL. The cases included 17 pleural, 2 peritoneal, and 2 pericardial fluid samples. Both T-LBL/ALL and B-LBL/ALL in SE exhibit a blast-like morphology, characterized by small to medium size, irregular nuclear membranes, and inconspicuous nucleoli, alongside frequent nuclear fragmentation and apoptotic bodies. LBL/ALL express immaturity markers such as terminal deoxynucleotidyl transferase (7/17, 41.2%), CD10 (6/12, 50%), CD43 (8/8, 100%), and CD99 (6/6, 100%). T-LBL/ALL and B-LBL/ALL specifically express T-cell markers (CD2 [3/6, 50%], CD3 [10/12, 83.3%], CD5 [2/11, 18.2%], CD7 [10/10, 100%]) or B-cell markers (CD20 [3/5, 60%], CD79a [4/4, 100%], PAX5 [5/5, 100%]), respectively. A high proportion of primitive and immature lymphocytes exceeding 25% in BM was observed in T-LBL/ALL (5/7) and in one case of B-LBL/ALL. No BCR/ABL gene rearrangements were detected in any cases. Furthermore, fusion gene MLL::ENL and PLCALM::MLLT10, as well as mutations in genes including WT1, NOTCH1, PAX5, IKZF, ARID1A, BCOR, SETD2, ARID2, TET2, JAK3, NF1, and CEBPA, were identified in LBL/ALL through RT-PCR, NGS, or WTS analyses.

[CONCLUSION] The integration of clinical manifestations, cytological evaluation, and gene expression profiles is instrumental in achieving accurate diagnosis, subclassification, and prognosis of LBL/ALL within the context of SE.