Molecular Progression of Myeloproliferative and Myelodysplastic/Myeloproliferative Neoplasms: A Study on Sequential Bone Marrow Biopsies

Clonal dynamics of chronic myelomonocytic leukemia progression: paired-sample comparison

This study investigated the clonal evolution of chronic myelomonocytic leukemia (CMML) progression to secondary acute myeloid leukemia (sAML) by next-generation sequencing and pyrosequencing for variant allele frequency (VAF) of gene mutations and SNP microarray for copy neutral loss of heterozygosity (CN-LOH) in 38 paired samples from CMML/sAML patients of Taiwanese origin. The median interval between CMML and sAML samples collection was 14.9 months (1.0-89.6). RUNX1 (57%), TET2 (46%), SRSF2 (37%), and ASXL1 (28%) mutations were frequent at CMML diagnosis. Baseline VAF in epigenetic regulator genes was high (>35%) in 83% of mutational events at the CMML phase, remained stable in 78% (VAF changes <10%), and increased in 20% (increased VAF > 10%) during progression to sAML. Transcription factor genes showed high VAF (>35%) in 51% at the CMML phase, and stable VAF in 60% during progression. VAF of spliceosome genes was high (>35%) in 70% at CMML phase, and stable in 61% during progression. Activated signaling genes exhibited acquisition or loss during progression. TET2 mutations were often founding clones, and SRSF2, ASXL1, DNMT3A, EZH2, or spliceosome genes also acted as ancestral mutations. RUNX1 mutations were typically later events and occasionally ancestral hits or germline mutations. Acquisition of cytogenetic changes, signaling pathways genes (PTPN11, FLT3, NRAS, CBL), or AML-defined genes (NPM1, CEBPA, CBFB::MYH11) by linear or branching evolution occurred during sAML progression. CN-LOH was noted in EZH2, CBL, TET2, and DNMT3A genes. CEBPA mutation and concurrent biallelic TET2 with NRAS mutations at CMML diagnosis were risk factors for time to AML progression and overall survival. A characteristic ASXL1MT/RUNX1MT/SpliceosomeMT/signalingWT genetic profile was associated with monocyte counts of 0.5-1.0 × 109/l. This study highlights the complexity and heterogeneity of dynamic changes in clonal architecture during CMML progression, emphasizing its importance in pathogenesis, phenotype, risk stratification, and therapeutic strategy. © 2025 The Pathological Society of Great Britain and Ireland.

A significant proportion of classic Hodgkin lymphoma recurrences represents clonally unrelated second primary lymphoma

Despite high cure rates in classic Hodgkin lymphoma (cHL), relapses are observed. Whether relapsed cHL represents second primary lymphoma or an underlying T-cell lymphoma (TCL) mimicking cHL is underinvestigated. To analyze the nature of cHL recurrences, in-depth clonality testing of immunoglobulin (Ig) and T-cell receptor (TCR) rearrangements was performed in paired cHL diagnoses and recurrences among 60 patients, supported by targeted mutation analysis of lymphoma-associated genes. Clonal Ig rearrangements were detected by next-generation sequencing (NGS) in 69 of 120 (58%) diagnoses and recurrence samples. The clonal relationship could be established in 34 cases, identifying clonally related relapsed cHL in 24 of 34 patients (71%). Clonally unrelated cHL was observed in 10 of 34 patients (29%) as determined by IG-NGS clonality assessment and confirmed by the identification of predominantly mutually exclusive gene mutations in the paired cHL samples. In recurrences of >2 years, ∼60% of patients with cHL for whom the clonal relationship could be established showed a second primary cHL. Clonal TCR gene rearrangements were identified in 14 of 125 samples (11%), and TCL-associated gene mutations were detected in 7 of 14 samples. Retrospective pathology review with integration of the molecular findings were consistent with an underlying TCL in 5 patients aged >50 years. This study shows that cHL recurrences, especially after 2 years, sometimes represent a new primary cHL or TCL mimicking cHL, as uncovered by NGS-based Ig/TCR clonality testing and gene mutation analysis. Given the significant therapeutic consequences, molecular testing of a presumed relapse in cHL is crucial for subsequent appropriate treatment strategies adapted to the specific lymphoma presentation.

Progression in Myeloid Neoplasms: Beyond the Myeloblast

Disease progression in myelodysplastic syndromes (MDS), myelodysplastic-myeloproliferative neoplasms (MDS/MPN), and myeloproliferative neoplasms (MPN), altogether referred to as myeloid neoplasms (MN), is a major source of mortality. Apart from transformation to acute myeloid leukemia, the clinical progression of MN is mostly due to the overgrowth of pre-existing hematopoiesis by the MN without an additional transforming event. Still, MN may evolve along other recurrent yet less well-known scenarios: (1) acquisition of MPN features in MDS or (2) MDS features in MPN, (3) progressive myelofibrosis (MF), (4) acquisition of chronic myelomonocytic leukemia (CMML)-like characteristics in MPN or MDS, (5) development of myeloid sarcoma (MS), (6) lymphoblastic (LB) transformation, (7) histiocytic/dendritic outgrowths. These MN-transformation types exhibit a propensity for extramedullary sites (e.g., skin, lymph nodes, liver), highlighting the importance of lesional biopsies in diagnosis. Gain of distinct mutations/mutational patterns seems to be causative or at least accompanying several of the above-mentioned scenarios. MDS developing MPN features often acquire MPN driver mutations (usually JAK2), and MF. Conversely, MPN gaining MDS features develop, e.g., ASXL1, IDH1/2, SF3B1, and/or SRSF2 mutations. Mutations of RAS-genes are often detected in CMML-like MPN progression. MS ex MN is characterized by complex karyotypes, FLT3 and/or NPM1 mutations, and often monoblastic phenotype. MN with LB transformation is associated with secondary genetic events linked to lineage reprogramming leading to the deregulation of ETV6, IKZF1, PAX5, PU.1, and RUNX1. Finally, the acquisition of MAPK-pathway gene mutations may shape MN toward histiocytic differentiation. Awareness of all these less well-known MN-progression types is important to guide optimal individual patient management.