Top Chromosomal Translocations for MRCP Part 1

TL;DR

For MRCP Part 1, recognising recurrent chromosomal translocations is an essential scoring opportunity because these abnormalities are strongly associated with specific haematological malignancies and sarcomas. List: Top 20 Chromosomal Translocations (t9;22) is a high-yield revision topic that repeatedly appears in examination questions. Learn the hallmark disease associations, important fusion genes, and common examination traps rather than attempting to memorise isolated chromosome numbers.

Why this matters

Chromosomal translocations represent one of the highest-yield genetics topics in MRCP Part 1. Rather than testing molecular biology in isolation, the examination typically presents a clinical vignette describing a patient with leukaemia, lymphoma or sarcoma before asking you to identify the underlying chromosomal abnormality.

The ability to rapidly recognise classic translocations can help answer questions on:

• Haematological malignancies

• Molecular diagnosis

• Targeted therapy

• Prognosis

• Cancer genetics

The Philadelphia chromosome (t(9;22)) is the best-known example, but several other transights frequently appear in MRCP examinations.

The 20 highest-yield chromosomal translocations

Translocation	Disease	Key fusion gene / Note	MRCP importance
t(9;22)	Chronic myeloid leukaemia (CML)	BCR-ABL1	Extremely high
t(9;22)	Adult ALL (subset)	BCR-ABL1	Very high
t(15;17)	Acute promyelocytic leukaemia	PML-RARA	Extremely high
t(8;21)	AML	RUNX1-RUNX1T1	High
inv(16) or t(16;16)	AML M4Eo	CBFB-MYH11	High
t(14;18)	Follicular lymphoma	BCL2	Very high
t(8;14)	Burkitt lymphoma	MYC	Extremely high
t(11;14)	Mantle cell lymphoma	Cyclin D1	Very high
t(11;18)	Gastric MALT lymphoma	API2-MALT1	Moderate
t(2;5)	Anaplastic large-cell lymphoma	ALK fusion	High
t(X;18)	Synovial sarcoma	SS18 fusion	Moderate
t(11;22)	Ewing sarcoma	EWSR1-FLI1	High
t(12;21)	Childhood ALL	ETV6-RUNX1	Moderate
t(1;19)	Pre-B ALL	TCF3-PBX1	Moderate
t(6;9)	AML	DEK-NUP214	Lower frequency
t(3;3)	AML	MECOM activation	Lower frequency
t(5;14)	T-cell ALL	IL3 activation	Rare
t(4;11)	Infant ALL	KMT2A rearrangement	High-yield concept
t(14;16)	Multiple myeloma	MAF	Moderate
t(4;14)	Multiple myeloma	FGFR3/MMSET	High

The five most tested translocations

1. t(9;22) — Philadelphia chromosome

This is by far the most important chromosomal abnormality for MRCP Part 1.

Key facts:

• Seen in approximately 95% of chronic myeloid leukaemia.

• Produces the BCR-ABL1 tyrosine kinase.

• Causes uncontrolled myeloid proliferation.

• Targeted treatment is with tyrosine kinase inhibitors such as imatinib.

• Also found in a proportion of adult acute lymphoblastic leukaemia.

Exam pearl: If a stem describes marked neutrophilia, basophilia, splenomegaly and a low leucocyte alkaline phosphatase score, immediately think of t(9;22).

2. t(15;17)

Acute promyelocytic leukaemia (APL) is another classic examination favourite.

Important features include:

• PML-RARA fusion

• Promyelocyte accumulation

• High risk of disseminated intravascular coagulation

• Responds dramatically to all-trans retinoic acid (ATRA)

This is considered a medical emergency.

3. t(8;14)

This translocation activates the MYC oncogene.

Associated with:

• Burkitt lymphoma

• "Starry sky" histology

• EBV association in endemic disease

• Very high proliferative rate

4. t(14;18)

Hallmark abnormality of follicular lymphoma.

Key concept:

• Overexpression of BCL2

• Inhibition of apoptosis

• Indolent clinical course

5. t(11;14)

Characteristic finding in mantle cell lymphoma.

Remember:

• Cyclin D1 overexpression

• Usually CD5 positive

• Aggressive behaviour compared with follicular lymphoma

Practical study outline

When revising chromosomal abnormalities, learn each translocation in the same structured format:

1. Chromosome numbers

2. Associated malignancy

3. Fusion gene

4. Molecular mechanism

5. Clinical significance

6. Targeted treatment (if applicable)

7. Prognosis

8. Classic examination clues

9. Important differentials

10. Memory aid or mnemonic

This approach makes recall considerably easier than memorising chromosome numbers alone.

Five common examination traps

Trap 1

Confusing t(9;22) with t(8;21).

Remember:

• t(9;22) = CML

• t(8;21) = AML

Trap 2

Mixing up follicular lymphoma and mantle cell lymphoma.

• Follicular lymphoma → t(14;18)

• Mantle cell lymphoma → t(11;14)

Trap 3

Assuming every acute leukaemia has the Philadelphia chromosome.

Only selected ALL cases have t(9;22); it is not the hallmark abnormality of AML.

Trap 4

Forgetting targeted therapies.

Questions increasingly link genetics with treatment:

• BCR-ABL → Imatinib

• PML-RARA → ATRA

Trap 5

Ignoring clinical presentation.

The diagnosis should come from the patient history first, with the translocation confirming your reasoning.

Practical examples / mini-cases

Mini-case

A 52-year-old man presents with fatigue, early satiety and weight loss. Examination reveals splenomegaly. Blood tests demonstrate:

• WCC: 160 × 10⁹/L

• Basophilia

• Neutrophilia

• Platelets mildly elevated

Which chromosomal abnormality is most likely?

Answer: t(9;22)

Explanation

The presentation is classic for chronic myeloid leukaemia. The Philadelphia chromosome produces the BCR-ABL tyrosine kinase, which drives uncontrolled proliferation of myeloid cells. Recognition of this abnormality also predicts response to tyrosine kinase inhibitors.

Practical study-tip checklist

Before your MRCP examination, ensure you can:

• ✓ Recognise the Philadelphia chromosome

• ✓ Identify the four classic lymphoma translocations

• ✓ Match AML subtypes with characteristic cytogenetics

• ✓ Recall the fusion genes for common translocations

• ✓ Link molecular abnormalities with targeted therapies

• ✓ Differentiate ALL from AML abnormalities

• ✓ Recognise sarcoma-associated translocations

• ✓ Interpret examination vignettes rather than isolated genetics

• ✓ Practise recall using flashcards

• ✓ Test yourself using timed MCQs

Regular practice with genetics questions is far more effective than passive reading. Reinforce these concepts using the MRCP Part 1 overview (https://www.crackmedicine.co.uk/mrcp-part-1/), complete Free MRCP MCQshttps://www.crackmedicine.com/qbank and assess your progress with Start a mock test https://www.crackmedicine.com/mock-tests.

FAQs

Which chromosomal translocation is most important for MRCP Part 1?

The Philadelphia chromosome, t(9;22), is the highest-yield translocation because of its association with chronic myeloid leukaemia and targeted therapy with tyrosine kinase inhibitors.

Is t(9;22) found only in chronic myeloid leukaemia?

No. Although it is the hallmark abnormality of CML, it is also identified in a proportion of adult acute lymphoblastic leukaemia and has prognostic and therapeutic significance.

Which translocation is associated with Burkitt lymphoma?

Burkitt lymphoma is classically associated with t(8;14), resulting in activation of the MYC oncogene.

Which translocation should make you think of acute promyelocytic leukaemia?

The characteristic abnormality is t(15;17), producing the PML-RARA fusion protein. Prompt recognition is essential because early treatment with ATRA reduces the risk of fatal haemorrhage.

Do I need to memorise all chromosomal translocations for MRCP Part 1?

No. Focus first on the highest-yield abnormalities that repeatedly appear in examination questions, particularly those associated with common haematological malignancies and targeted treatments.

Ready to start

Build confidence in genetics and haematology by practising clinically focused questions rather than memorising isolated facts. Use Crack Medicine's MRCP Part 1 overview, Free MRCP MCQs, mock tests, and video lectures to reinforce high-yield translocations through repeated examination-style practice.

Sources

1. MRCP(UK). https://www.mrcpuk.org/

2. World Health Organization. Classification of Haematolymphoid Tumours.

3. National Comprehensive Cancer Network (NCCN). Clinical Practice Guidelines in Oncology.

4. European Society for Medical Oncology (ESMO). Haematological Malignancy Guidelines.

5. Hoffbrand AV, Moss PAH. Essential Haematology. Wiley-Blackwell.

6. Bain BJ. Blood Cells: A Practical Guide. Wiley-Blackwell.