A MYC rearrangement test looks for a structural change that places the MYC gene next to a powerful regulatory region, causing excessive MYC activity and rapid cell growth. It is most often used in aggressive B-cell lymphomas, including diffuse large B-cell lymphoma (DLBCL), high-grade B-cell lymphoma, and suspected Burkitt lymphoma. Testing is commonly performed with fluorescence in situ hybridization (FISH) on a lymph node, mass biopsy, bone marrow, or another tumor sample. The result becomes especially important when MYC is rearranged together with BCL2, a pattern that defines a distinct high-grade lymphoma category in current classifications. BCL6 may also be tested, but MYC plus BCL6 without BCL2 is interpreted differently. A positive MYC result does not provide the full diagnosis, and a negative result does not mean the lymphoma is slow-growing. Pathologists combine morphology, immunophenotype, MYC and BCL2 protein expression, cytogenetics, and clinical findings before assigning a final classification and treatment plan.
- MYC FISH detects a gene rearrangement, not simply high MYC protein expression.
- MYC plus BCL2 rearrangements are often called “double hit” and carry distinct diagnostic and treatment implications.
- A “double expresser” lymphoma has high MYC and BCL2 proteins by immunohistochemistry but may have no rearrangement.
- A negative MYC FISH result does not exclude aggressive lymphoma or MYC activation by another mechanism.
- Adequate tumor tissue and correct probe selection are essential for a reliable result.
Table of Contents
- What a MYC Rearrangement Means
- When MYC Testing Is Needed
- How FISH and Other Methods Work
- Reading the Result
- Double-Hit, Triple-Hit, and Double-Expresser Lymphoma
- MYC in Burkitt Lymphoma and Other Cancers
- Treatment, Prognosis, and Next Steps
- Limitations and Questions to Ask
What a MYC Rearrangement Means
MYC is a transcription factor that controls genes involved in cell growth, metabolism, division, and survival. Normal cells regulate MYC tightly. In a rearranged tumor, a chromosome break moves MYC, located at 8q24, beside an active enhancer from another gene. Immunoglobulin genes are frequent partners because B cells naturally activate these regions while making antibodies. Common examples include IGH::MYC from t(8;14), IGK::MYC, and IGL::MYC, although non-immunoglobulin partners also occur.
The rearrangement is an acquired, or somatic, tumor change. It is not usually inherited and does not mean relatives carry a MYC cancer-risk mutation. The test examines tumor cells, not constitutional DNA. Rare inherited syndromes can influence lymphoma risk through other genes, but routine MYC FISH is not a hereditary cancer test.
A rearrangement can accelerate an already abnormal B-cell clone. Its meaning depends on the lymphoma in which it appears. In Burkitt lymphoma, an IG::MYC rearrangement is characteristic, but diagnosis also requires the expected morphology, immunophenotype, very high proliferation, and overall molecular context. In DLBCL or high-grade B-cell lymphoma, MYC rearrangement may occur alone or with BCL2 or BCL6 rearrangements.
Current classification gives special status to lymphomas with both MYC and BCL2 rearrangements. The exact terminology has changed across the World Health Organization and International Consensus Classification systems. As a result, a report should state the actual findings rather than relying only on an older label such as “double-hit lymphoma.” The pathologist should identify which genes are rearranged, the morphology, and the classification framework being used.
MYC protein overexpression is related but not identical. Immunohistochemistry stains tumor cells for MYC protein and reports the approximate percentage positive. High expression may result from a rearrangement, copy-number gain, signaling pathway activation, or other mechanisms. FISH answers a structural-genetic question; immunohistochemistry answers a protein-expression question.
When MYC Testing Is Needed
MYC testing is most commonly ordered when a biopsy shows a large B-cell or high-grade B-cell lymphoma. Many centers perform FISH for MYC, BCL2, and BCL6 broadly in newly diagnosed DLBCL because morphology and immunohistochemistry do not reliably identify all rearranged cases. Other laboratories use a screening strategy based on high-grade morphology, germinal-center phenotype, MYC/BCL2 protein expression, unusual clinical features, or pathologist judgment.
Testing is particularly important when the tumor has:
- blastoid or Burkitt-like cytology;
- an extremely high Ki-67 proliferation index;
- germinal-center B-cell markers such as CD10 or BCL6;
- strong MYC and BCL2 protein expression;
- widespread extranodal disease, marrow involvement, or central nervous system concern;
- morphology intermediate between DLBCL and Burkitt lymphoma;
- a prior indolent lymphoma that has transformed to an aggressive form.
A complete workup also includes histology, flow cytometry or immunohistochemistry, and staging. FISH is not a substitute for an adequate tissue biopsy. A fine-needle aspirate may show lymphoma cells, but a core or excisional biopsy often provides the architecture and sufficient material needed for classification. When tissue is limited, the pathology team prioritizes tests that will most affect diagnosis and treatment.
The clinician may request a BCL2 rearrangement test and a BCL6 rearrangement test with MYC. Results should be read together. MYC alone, MYC+BCL2, and MYC+BCL6 can represent biologically and clinically different groups.
MYC testing may also be used in acute lymphoblastic leukemia or other mature B-cell leukemias when morphology and immunophenotype suggest a MYC-rearranged process. It is not a routine test for every leukemia. In plasma-cell neoplasms and some solid tumors, MYC alterations can occur, but assay design and clinical implications differ from lymphoma testing.
How FISH and Other Methods Work
FISH is the standard targeted method for detecting MYC rearrangements in routine lymphoma practice. Fluorescent probes bind DNA near MYC. A break-apart probe uses differently colored signals on opposite sides of the gene. In normal cells, the signals remain together; separation beyond the laboratory’s validated distance supports a rearrangement. A dual-fusion probe tests a specific partner, such as IGH::MYC, by looking for fused signals from the two genes.
Break-apart probes detect a wider range of partners, while dual-fusion probes answer a more specific question. No single probe strategy captures every complex or cryptic event. Some laboratories begin with a MYC break-apart probe and add partner testing when clinically useful.
| Method | Result produced | Strength | Important limitation |
|---|---|---|---|
| Break-apart FISH | MYC rearranged or not detected | Works on fixed tissue and detects many partners | Does not always identify the partner |
| Dual-fusion FISH | Specific fusion such as IGH::MYC | Confirms a defined partner | Misses rearrangements with other partners |
| Karyotype | Chromosome-level translocation | Shows broader cytogenetic context | Requires dividing cells and may miss cryptic changes |
| DNA-based NGS | Selected structural variants and mutations | Profiles many genes together | Some panels poorly cover MYC breakpoints |
| RNA sequencing | Expressed fusion transcript | Can identify partners and confirm expression | RNA quality in fixed tissue may be poor |
The laboratory counts a defined number of tumor nuclei and compares the abnormal signal percentage with a validated cutoff. A report may state, for example, that a rearrangement pattern was present in a certain percentage of nuclei. This percentage is not the chance of responding to treatment and should not be read as a survival estimate. It reflects the sampled cells and assay scoring.
Preanalytic quality matters. Decalcified bone marrow, crushed tissue, necrosis, scant tumor, or prolonged fixation can reduce signal quality. The pathologist marks a tumor-rich region so the laboratory does not count mostly benign cells. A technically inadequate result may require another block, a different specimen, or an alternative method.
Reading the Result
A report that says MYC rearrangement detected means the assay found a structural break meeting its validated criteria. The next questions are whether BCL2 and BCL6 are rearranged, what the tumor looks like, and whether the rearrangement partner is known. “MYC rearranged” is a biomarker result, not a complete lymphoma name.
A MYC rearrangement not detected result means the assay did not find the targeted abnormal signal above its threshold. It does not exclude high MYC protein, MYC copy-number gain, a cryptic rearrangement outside probe coverage, or an aggressive lymphoma driven by other changes. The report should be interpreted in light of tumor content and probe performance.
An equivocal result can occur when the abnormal signal percentage is close to the cutoff, nuclei are damaged, the tissue has overlapping cells, or the pattern is atypical. The pathologist may recount the slide, test another block, use a partner probe, perform sequencing, or integrate the result conservatively. Treatment should not be escalated on a questionable signal pattern without review.
Some reports describe copy-number gain or amplification rather than rearrangement. Extra MYC signals may reflect chromosome 8 gain, regional amplification, or a complex genome. These findings can have biological significance but do not meet the definition of a MYC rearrangement and should not automatically be called a “hit.”
The phrase variant rearrangement may indicate a non-immunoglobulin partner. Partner identity can influence biology in some studies, but it does not replace the established classification based on MYC and BCL2 status, morphology, and other features. Ask whether the partner was directly demonstrated or only inferred.
Double-Hit, Triple-Hit, and Double-Expresser Lymphoma
“Double hit” historically described an aggressive B-cell lymphoma with MYC plus BCL2 and/or BCL6 rearrangements. Modern classifications are more precise. Lymphomas with MYC and BCL2 rearrangements form a recognized high-grade category when the morphology fits. A BCL6 rearrangement may also be present, producing the traditional “triple-hit” pattern of MYC+BCL2+BCL6.
MYC+BCL6 without BCL2 is no longer automatically grouped with MYC+BCL2 in the WHO fifth edition. Depending on morphology, it may be classified as DLBCL, not otherwise specified, or high-grade B-cell lymphoma, not otherwise specified. The International Consensus Classification handles some categories differently. The pathology report should therefore provide gene-level results and not leave clinicians to infer biology from an umbrella term.
A double-expresser lymphoma is defined by immunohistochemical co-expression of MYC and BCL2 proteins, often using thresholds around 40% for MYC and 50% for BCL2, although laboratory practice and studies vary. Double expression is more common than double-hit genetics. It can carry adverse prognostic information in some settings, but it is not the same entity and cannot substitute for FISH.
| Term | How it is measured | Typical finding |
|---|---|---|
| MYC rearranged | FISH or structural-variant assay | A chromosome break involving MYC |
| Double hit | FISH or equivalent genetics | MYC plus BCL2 rearrangements in current core usage |
| Triple hit | FISH or equivalent genetics | MYC, BCL2, and BCL6 rearrangements |
| Double expresser | Immunohistochemistry | High MYC and BCL2 protein expression |
These distinctions affect communication and may affect therapy. A patient should ask for the actual FISH findings rather than relying on a shorthand phrase in a clinic note.
MYC in Burkitt Lymphoma and Other Cancers
Burkitt lymphoma is a rapidly growing mature B-cell lymphoma with a characteristic starry-sky appearance, medium-sized cells, germinal-center phenotype, nearly 100% Ki-67, and a MYC rearrangement in most cases. The classic partner is IGH at chromosome 14, but light-chain partners occur. Epstein-Barr virus association varies by epidemiologic setting.
A MYC rearrangement alone does not prove Burkitt lymphoma. Some DLBCLs and high-grade B-cell lymphomas carry the same genetic event. Conversely, rare tumors with otherwise convincing Burkitt features may lack a demonstrable MYC rearrangement and require assessment for alternative molecular entities. Pathology expertise is essential because treatment approaches differ.
MYC rearrangements can also appear in transformed follicular lymphoma, mantle cell lymphoma, plasmablastic lymphoma, plasma-cell myeloma, and other uncommon contexts. In each, the meaning is shaped by the underlying disease. A MYC event acquired during transformation may signal clonal evolution and more aggressive behavior, but it does not erase the lineage established by morphology and immunophenotype.
In leukemia presentations, tumor cells may circulate in blood or dominate marrow. The same FISH principle applies, but the differential diagnosis can include Burkitt leukemia/lymphoma, B-lymphoblastic leukemia with MYC rearrangement, and other high-grade neoplasms. Cell maturity, surface immunoglobulin, terminal deoxynucleotidyl transferase, cytogenetics, and molecular features separate these conditions.
MYC copy-number changes and expression are also studied across solid tumors. Those findings are not interpreted with lymphoma “double-hit” rules. A test ordered for a solid tumor should use disease-specific evidence and reporting standards rather than borrowing terminology from B-cell lymphoma.
Treatment, Prognosis, and Next Steps
MYC rearrangement can identify a lymphoma with high-risk biology, but treatment is not selected from the MYC result alone. The final diagnosis, MYC/BCL2 combination, stage, age, organ function, performance status, central nervous system risk, and treatment goals all matter. Clinical guidelines and specialist judgment determine whether standard immunochemotherapy or a more intensive regimen is appropriate.
Historically, MYC+BCL2-rearranged lymphomas have had poor outcomes with standard R-CHOP in retrospective series, leading many centers to consider dose-adjusted EPOCH-R or other intensive approaches for fit patients. Evidence is not identical across all subgroups, and no regimen is universally best for every patient. Older or medically frail patients may not tolerate intensive treatment. Clinical trials are especially valuable because classification and therapies continue to evolve.
Burkitt lymphoma requires prompt, intensive, central nervous system-penetrating therapy rather than a routine DLBCL approach. A suspected diagnosis is often managed urgently because tumor burden can rise quickly and tumor lysis syndrome can occur. Treatment planning includes hydration, uric-acid management, and close laboratory monitoring.
Prognosis should not be reduced to “MYC positive equals bad.” Outcomes differ between single-hit MYC, MYC+BCL2, partner types, morphologic categories, stages, and treatment regimens. International Prognostic Index variables, response on PET/CT, molecular subtype, and ability to complete therapy also matter. The percentage of FISH-positive nuclei is not a validated personal survival calculator.
After the result, the usual sequence is pathology integration, staging imaging, laboratory assessment, possible marrow or cerebrospinal-fluid evaluation, risk discussion, and treatment planning. Because the terminology changed recently, a second pathology review can be useful when the report uses an older category or when FISH and morphology appear discordant.
Limitations and Questions to Ask
FISH is targeted and depends on probe design. A MYC break-apart assay can miss unusual cryptic events; a dual-fusion assay can miss alternate partners. Complex signal patterns may be hard to classify. DNA sequencing panels may also miss rearrangements when intronic breakpoint regions are not captured. RNA sequencing can help, but degraded RNA is common in fixed tissue.
Tumor heterogeneity creates another limitation. A small biopsy may not sample every clone. A transformed site can carry a MYC rearrangement that was absent from an earlier indolent biopsy. Retesting may be appropriate when disease behavior changes or a new biopsy shows higher-grade morphology.
Ask the care team:
- Was MYC tested with a break-apart probe, a partner-specific probe, or sequencing?
- Were BCL2 and BCL6 also tested, and what were their exact results?
- Is this MYC rearrangement single hit, MYC+BCL2, MYC+BCL6, or triple hit?
- Is MYC protein also overexpressed, and does the tumor meet double-expresser criteria?
- What is the final WHO or ICC diagnosis after integrating all results?
- Is the specimen adequate, or was any result equivocal?
- Does the finding change the treatment regimen or central nervous system evaluation?
- Would expert hematopathology review or a clinical trial be appropriate?
Keep the original pathology report, FISH addendum, immunohistochemistry, and any sequencing report together. A summary that says only “MYC positive” loses important distinctions. The most actionable record states the specimen, morphology, MYC method, partner if known, BCL2/BCL6 status, and final integrated diagnosis.
How an integrated lymphoma report should read
The final diagnosis should bring several layers together in one coherent statement. Morphology establishes whether the cells resemble DLBCL, Burkitt lymphoma, or another high-grade process. Immunophenotype confirms mature B-cell lineage and records markers such as CD10, BCL6, MUM1, BCL2, MYC, Ki-67, and sometimes terminal deoxynucleotidyl transferase. FISH then specifies MYC, BCL2, and BCL6 status. A report that lists these tests separately without an integrated classification leaves an important clinical task unfinished.
The specimen date and disease phase also matter. A MYC-negative low-grade follicular lymphoma biopsy from several years earlier cannot substitute for testing a newly transformed rapidly growing mass. Transformation may be spatially heterogeneous, so the most metabolically active or clinically aggressive site is often the best biopsy target. If only marrow is available, the team should ask whether the tested cells represent the same high-grade component seen elsewhere.
Staging and immediate safety assessment proceed while molecular testing is finalized. Baseline lactate dehydrogenase, kidney and liver function, uric acid, hepatitis screening, echocardiography when anthracycline is planned, PET/CT, and fertility discussion may be needed. A very high tumor burden can cause spontaneous or treatment-related tumor lysis syndrome. Preventive hydration, uric-acid lowering therapy, and frequent electrolytes may begin before the exact double-hit classification is complete.
When seeking a second opinion, send the actual slides or tissue block, FISH signal images or report, flow-cytometry data, and all immunostains—not only the diagnosis line. Experts can resolve whether an atypical signal represents a true rearrangement, whether the morphology meets the current entity, and whether older terminology should be updated. This review can be especially valuable before an intensive regimen, stem cell strategy, or trial enrollment.
Response assessment is separate from baseline genetics. PET/CT after therapy evaluates metabolic response, while persistent masses can represent scar tissue. Routine serial MYC FISH in blood is not a standard MRD test for most DLBCL. A new enlarging lesion usually requires imaging and sometimes biopsy rather than assuming molecular relapse from the original result.
The treatment discussion should include supportive care as well as regimen intensity. Growth-factor support, infection prevention, transfusion planning, fertility preservation, and central nervous system prophylaxis or evaluation may be considered. The MYC result can increase concern for aggressive behavior, but CNS decisions use an established risk model, disease sites, kidney or adrenal involvement, and the final lymphoma category rather than MYC status alone.
If the patient has received corticosteroids before biopsy, the tissue can show partial tumor destruction and lower FISH yield. Pathologists should know the medication timing. When possible, another viable site may provide a more definitive diagnosis, but urgent treatment should not be delayed in an unstable patient solely to obtain an ideal specimen.
In relapsed disease, a new biopsy can be more informative than repeating FISH on an old block. It confirms viable lymphoma, excludes infection or another cancer, and shows whether the molecular profile has evolved. Trial eligibility may depend on current CD19, CD20, or other target expression in addition to the original MYC result.
References
- Large B-cell lymphoma (LBCL): EHA Clinical Practice Guidelines for diagnosis, treatment, and follow-up 2025 (Guideline)
- The high-grade B-cell lymphomas: double hit and more 2024 (Review)
- Double hit lymphoma: contemporary understanding and future perspectives 2025 (Review)
- A retrospective study of MYC rearranged diffuse large B-cell lymphoma in the context of the new WHO and ICC classifications 2023 (Cohort Study)
- Aggressive B-Cell Non-Hodgkin Lymphoma Treatment (PDQ®) 2025 (Official Review)
Disclaimer
This article offers general information about MYC rearrangement testing and cannot establish a lymphoma diagnosis or select a treatment regimen. Interpretation requires the full biopsy, BCL2/BCL6 testing, staging, and review by hematopathology and oncology specialists. Rapidly progressive symptoms or suspected high-grade lymphoma require prompt medical care.
