Hematologic malignancies are myeloid and lymphatic tumors caused by a disruption of normal hematopoietic function (1). This heterogenous group of diseases differs in cellular origin and clinical manifestation. Classification system combines clinical, pathologic, and molecular features of the diseases. In general, they can be divided into leukemias and lymphomas. While leukemias involve peripheral blood and are composed of immature hematopoietic elements lymphomas are composed of B-cells, T-cells or natural killer cells of varying degrees of maturity that mainly affect solid tissues or lymph nodes (2).
Cytogenetics and targeted molecular assays are now routine and necessary for the diagnosis and prognostication of most myeloid neoplasms. Molecular methods to detect specific mutations include sequencing methods (Sanger or Next-Generation Sequencing (NGS) gene panels) or modified polymerase chain reaction (PCR) techniques using genomic DNA. Most hematologic neoplasms require the analysis of chromosomal abnormalities to detect gene fusions and rearrangements by karyotype and/or fluorescence in situ hybridization (FISH) or RNA-based PCR assays may be performed, which does not require amplification of large intronic regions. After the initiation of the treatment, quantitative PCR (qPCR) or digital droplet PCR (ddPCR) assay may be used to asses for response to therapy, measured by the decrease in fusion protein transcript level. Measurable residual disease (MRD) is an important biomarker that is used for prognostic, predictive, monitoring, and efficacy-response assessments (3).
These neoplasms can be classified as Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). B-cell NHL is far more common than T-cell or NK-cell NHL and comprises approximately 80 % of lymphomas in Europe. Usually they are very heterogenous in their etiology and pathogenesis, but many are derived from the germinal center reaction (2).
CLL/SLL (Small lymphocytic lymphoma) is defined as a monoclonal lymphoproliferative disease characterized by the proliferation and accumulation of morphologically mature but immunologically dysfunctional B-cell lymphocytes (4).
The most frequently mutated genes in CLL are
Recurrent mutations and genetic alterations in mature lymphoid neoplasms
BNHL | Molecular alterations | Risk stratification |
---|---|---|
B-CLL/SLL | del 13q, 11q, 17p13, 6q21, trisomy 12 | |
Burkitt lymphoma | translocation at 8q24 ( |
|
DLBCL | rearrangements |
16q22-q24, 6p21-p25, 12q22-q24, 11q23-q25, 19q13, 1q21-q23, 8q24, and 19p13, and -17 appeared to be associated with a worse prognosis (30) |
Follicular lymphoma | t(14;18), abnormalities |
deletions of 1p, 6q, and 17p, and gains of 7 and 12q are strongly associated with a poor prognosis also correlate with a higher risk of transformation (31) |
Hairy cell leukemia | ||
MALT lymphoma | t(11;18), t(14;18)(q32;q21), t(3;14) | |
Mantle cell lymphoma | t(11;14)(q13;q32) |
BL is an aggressive B-cell lymphoma characterized by a high degree of proliferation of the malignant cells and deregulation of the c
DLBCL represent a group of aggressive B-cell lymphomas with underlying genetic diversity and variable clinical presentations. Based on cell-of-origin several subtypes of DLBCL were identified: GCB – Germinal center B-cell, ABC – activated B-cell, PMBL – primary mediastinal B-cell, and 15–20% of cases are unclassified. The 2016 revision of the World Health Organization (WHO) classification recognized and introduced a new entity, highgrade B-cell lymphoma (HGBCL), defined by the presence of
MCL is a B-cell neoplasm characterized by the expansion of mature B cells frequently coexpressing CD5 that tend to widely spread in bone marrow, blood, lymphoid tissues, and extranodal sites. The tumor cells carry the t(11;14)(q13;q32) that leads to the constitutive overexpression of cyclin D1. Cryptic rearrangements of IG regulatory regions could be an alternative oncogenic mechanism in a minor subgroup of patients (10).
FL is considered as the most common indolent B cell lymphoma. Histologically is characterized by a follicular or nodular pattern of tumor cell growth. More than 85% of FL cases harbor the characteristic t(14;18)(q32;q21), which occurs in pro- or pre-B cells of the bone marrow. Using sensitive techniques, the t(14;18) may be detected in B cells from peripheral blood and/or lymphoid tissues of a large proportion (up to 70%) of healthy individuals although the vast majority of them will never develop FL, indicating that
HCL is an uncommon chronic LPD characterized by progressive bone marrow failure due to infiltrating malignant B cells with “hairy-like surface projections” provoking frequent infectious complications (13). HCL comprises the clonal hematologic malignancies of classical (cHCL) and variant (vHCL). The mutations present in each HCL subtype are distinct, with
MALT lymphomas are a diverse group of lymphoid neoplasms with B-cell origin, occurring in adult patients and usually having an indolent clinical behavior. These lymphomas may arise in different anatomic locations, sharing many clinicopathological characteristics, but also having substantial variances in the aetiology and genetic alterations. MALT lymphomas can occur at any extranodal site. The most common anatomic sites are the stomach (30%), followed by eye/adnexa (12%), skin (10%), lung (9%), and salivary gland (7%). However, these lymphomas have been described at many other mucosal organs, such as thyroid, liver, small intestine, large intestine, bladder, dura, and many other sites. Chromosomal translocations are recurrent in MALT lymphomas with different prevalence among different sites, being the 4 most common: t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21), and t(3;14)(p14.1;q32). All these translocations and their products target the activation of nuclear factor k-light-chain-enhancer of activated B-cells (NF-kB) pathway. MALT lymphomas have highly altered variable heavy chain immunoglobulin (
MM is the second most common hematologic malignancy. Typical clinical symptoms of MM include bone destruction, hypercalcemia, renal failure, cytopenia, and immune paralysis. Symptomatic multiple myeloma can be preceded by 2 premalignant conditions called monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM), all of which share several genetic features. Translocations can be found in half of MGUS and MM patients. Most translocations involve the IgH locus (14q32), which puts oncogenes under the influence of the powerful IgH enhancer and thus result in upregulation. Translocations involving the immunoglobulin lambda (IgL) locus are present in 10% of patients with newly diagnosed MM and up to 20% in relapsed-refractory MM and are indicative of poor prognosis (table 2) (16). The most common result of IgH translocation is dysregulation of cyclin D (
Recurrent mutations and genetic alterations in multiple myeloma (16, 17).
Genetic abnormalities | Affected genes | Frequency | Prognosis |
---|---|---|---|
t(4;14) | 11-15% | High risk | |
t(6;14) | 1-2% | Standard risk | |
t(11;14) | 15% | Intedmerdiate risk | |
t(14;16) | 3-5% | High risk | |
t(14;20) | 1% | High risk | |
Del 1q | 30% | Shorter survival | |
Gain of 1q | 50% NDMM | Poor prognosis | |
Del 13q | 45% | del(13q) – independent favorable impact on OS monosomy 13 – shorter OS | |
Del 17p | 5-12% NDMM | Shorter survival | |
KRAS | ~ 50% | Neutral | |
NRAS | ~ 50% | Worse outcome | |
BRAF | ~ 50% | Negative influence on survival | |
EGR1 | ~ 50% | Favorable effect on outcomes |
Myeloid neoplasms are clonal hematopoietic proliferations representing a wide range of clinical, hematologic, genetic, and immunophenotypic properties and with a variable rate of genetic instability and clonal progression. Based on these properties, myeloid neoplasms are divided into 10 broad categories with more than 60 entities. Based on the complete blood count data (CBC) and blood smear morphology, myeloid neoplasms can be segregated into four broad disease categories – Acute myeloid leukemia (AML), Myelodysplastic syndrome (MDS), Myeloproliferative neoplasm (MPN), and Myelodysplastic/myeloproliferative neoplasm (MDS/MPN) (18).
MPNs are characterized by an excessive production of terminally differentiated blood cells that are fully functional. All MPN entities arise from a single somatically mutated hematopoietic stem cell (HSC) that clonally expands and gives rise to virtually all myeloid cells, and B and natural killer (NK) cells. The clonal expansion of the MPN HSC is accompanied by single or multilineage hyperplasia. Somatic mutations are responsible for the clonal expansion of HSCs not only in MPNs, but also in most types of myeloid malignancies (19). Among MPNs, chronic myeloid leukemia is characterized by the presence of Philadelphia chromosome (Ph) resulting from the translocation between chromosomes 9 and 22 [t(9;22)(q34;q11)] leading to BCR/ABL1 gene fusion. The Ph-negative MPNs encompass 3 clinical subtypes: polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). In contrast to chronic myeloid leukemia, disease-specific genetic abnormalities have not been detected that distinguish PV, ET, and PMF (20).
The Philadelphia chromosome, originating from a balanced reciprocal translocation MR4 (≥ 4 log reduction; ≤ 0.01%) MR4,5 (≥ 4, 5 log reduction; ≤ 0.0032%) MR5 (≥ 5 log reduction; ≤ 0.001%).
It is therefore important at the time of diagnosis to carry out an examination to determine the presence and determination of the amount of transcripts.
A major characteristic of Ph-negative MPNs is an increased signaling through the Janus kinase (JAK) signal transducer and activator of transcription (STAT) pathway as well as through the phosphatidylinositol 3-kinase (PI3K)-AKT (also known as protein kinase B) pathway in erythroid and myeloid cells. The most significant evidence of molecular pathology was reported in 2005 with the identification of the somatic mutation
Somatic activating mutations in the MPL virus oncogene
Mutations in calreticulin (
Recurrent mutations and genetic alterations in Ph negative myeloproliferative neoplasms (19)
Gene | Location | Mutation | Protein function | Frequency | Consequence |
---|---|---|---|---|---|
JAK2 | 9p24 | tyrosine kinase associated with cytokine receptors | 95% PV 50-60% PMF 50-60% ET | increased RBC, WBC, PLT production | |
3% PV | |||||
MPL | 1p34 | MPL515L/K/A/R MPLS505N | TPOR | 2-3% ET | increased PLT production |
other missense mutations | 3-5% PMF | ||||
CALR | 19p13 | indel exon 9 | Mutant: activator MPL | 20-25% ET 25-30% PMF | increased PLT production |
MDS are a heterogeneous group of hematopoietic precursor cell diseases with altered cell proliferation and maturation characterized by peripheral cytopenia due to ineffective hematopoiesis, dysplasia of one or more cell lineages, and an increased risk of transformation to acute myeloid leukemia (AML). The hallmark of MDS is bone marrow failure due to the growth of somatically mutated clonal hematopoietic stem cells (24). Karyotypic abnormalities are seen in approximately 30–50% of patients with MDS and correlated with prognosis. The most frequent cytogenetic abnormality in MDS is deletion 5q with frequency about 15%. Deletion 5q32-33 is frequently associated with 5q-syndrome and patients with this syndrome have a better overall survival and less risk of transformation to AML. But deletion 5q31is typically present in MDS that arose in connection with previous chemotherapy and has a more aggressive course with a high risk of progression to AML. Monosomy or deletion 7 is connected with a poor prognosis. Approximately 10% of MDS patients have an abnormality of the chromosome 7 either alone or as part of a complex karyotype. Abnormalities of the chromosome 7 occur in up to 50% of patients with MDS arising after the treatment with alkylating agents. Chromosome 7 abnormalities associated with 5q-or transcription factor
Recurrent mutations and genetic alterations in Myelodysplastic syndrome (24,25)
Cytogenetic alterations | Risk category |
---|---|
del(11q), -Y | Very good |
del(5q), del(12p), del(20q), double including del(5q), normal karyotype | Good |
del(7q), + 8, + 19, isochromosome i(17q), any other single or double independent clones | Intermediate |
-7, inv(3)/t(3q)/del(3q), double including - 7/del(7q), complex karyotype: > 3 alterations | Poor |
complex karyotype: > 3 alterations | Very poor |
Biallelic |
Very poor |
Favorable risk | |
Lower risk | |
Associated with chromosome 7 abnormalities |
AML is a heterogenous group of hematopoietic malignancies characterized by a proliferation of immature cells (blasts). Early classification systems were based on the morphologic features of these blasts, while in last two decades, the predominant classification systems by the World Health Organization (WHO) have increasingly incorporated immunophenotypic and genetic characteristics to refine these groupings. The 5th edition of the WHO classification evaluates three categories based on – (1) reccurent genetic abnormalities, (2) myelodysplasia-associated genetic changes, and (3) germline predisposition (26,27).
AML is a lethal disease and has a 5-year relative survival rate of 24.2%. However, the outcomes are heterogenous and the overall survival rates range from 5% to 70%. Thus, a need exists for prognostive markers to predict outcomes and guide therapeutic decisionmaking. The strongest prognostic factor for predicting therapeutic response and survival is cytogenetic subgrouping. Risk groups in AML were classified into three cathegories according to the 2022 European Leukemia Net (ELN) risk stratification based on genetics (Table 5) (28). Translocations t(15;17), t(8;21), inv16/ t(16;16), a normal karyotype and mutated
Risk groups in AML according to the European Leukemia Net risk stratification
Favorable risk | Intermediate risk | Adverse risk |
---|---|---|
t(8;21)(q22;q22.1)/ |
t(6;9)(p23;q34.1)/ |
|
inv(16)(p13.1;q22) | t(9;11)(p21.3;q23.3)/ |
t(v;11q23.3/ |
t(16;16)(p13.1;q22)/ |
cytogenetic and/or molecular abnormalities not classified as favorable or adverse | t(9;22)(q34.1;q11.2)/ |
mutated |
(8;16)(p11;p13)/ |
|
bZIP in-frame mutated |
inv(3)(q21.3;q26.2) or t(3;3)(q21.3;q26.2)/ |
|
t(3q26.2;v) |
||
monosomy 5 or del(5q) | ||
monosomy 7 | ||
monosomy 17/abn(17p) | ||
complex karyotype > 3 unrelated chromosomal abnormalities | ||
mutated |
||
mutated |
(26)
Molecular testing for t(15;17),
Most hematologic malignancies are clonal neoplasms and have specific somatic genetic and molecular characteristic which may influence therapeutic response and prognosis. The molecular basis of each tumor type is becoming essential to the diagnosis, in addition to determining therapy and prognosis. Understanding of the molecular pathogenesis of the diseases has improved, new therapeutic approaches have become crucial. Personalized therapeutic approaches assume prominence, emphasizing the need for tailored interventions based on individual patient characteristics. Incorporating cytogenetic changes alongise othe prognostic factors becomes crucial in determining the optimal treatment strategy. With expanding and increasing use of NGS panels, not just for detection of diagnostic gene mutations but also for detection of clonal lymfoid populations, chromosomal fusions, or minimal residual disease.