What cytogenetic abnormality is likely to be seen on analysis of a lymph node in a patient with follicular center cell lymphoma?

Cytogenetic Abnormality in Follicular Center Cell Lymphoma

The t(14;18)(q32;q21) translocation is the characteristic cytogenetic abnormality that would be seen on analysis of a lymph node in a patient with follicular center cell lymphoma (answer D).

Genetic Hallmark of Follicular Lymphoma

Follicular center cell lymphoma (also known as follicular lymphoma) has a distinctive genetic profile characterized by:

• The t(14;18)(q32;q21) translocation is present in approximately 85% of follicular lymphoma cases 1
• This translocation juxtaposes the BCL2 gene on chromosome 18 with the immunoglobulin heavy chain (IGH) locus on chromosome 14 2
• The resulting BCL2-IGH fusion leads to overexpression of the BCL2 protein, an anti-apoptotic protein that promotes cell survival 1

Diagnostic Testing Methods

Several techniques can be used to detect this characteristic translocation:

• Conventional cytogenetics: Can identify the t(14;18) in metaphase spreads
• Fluorescence in situ hybridization (FISH): Particularly useful for fixed, paraffin-embedded tissue samples 3
• Polymerase chain reaction (PCR): Can detect the molecular breakpoints 3

Differential Diagnosis of Cytogenetic Abnormalities

The other translocations listed in the question are associated with different hematologic malignancies:

• t(8;21): Typically seen in acute myeloid leukemia with maturation
• t(12;21): Associated with pediatric B-cell acute lymphoblastic leukemia
• t(8;14): Characteristic of Burkitt lymphoma 2
• t(9;22): Philadelphia chromosome seen in chronic myeloid leukemia and some acute leukemias

Clinical Significance

The detection of t(14;18) has important implications:

• Diagnostic value: Helps confirm the diagnosis of follicular lymphoma when histology is ambiguous 2
• Prognostic significance: While the t(14;18) itself doesn't strongly correlate with outcome, additional cytogenetic abnormalities may have prognostic implications 4
• Disease monitoring: Can be used to monitor minimal residual disease and response to therapy 3

Variant Translocations

It's worth noting that variant translocations involving BCL2 can also occur in follicular lymphoma:

• t(2;18)(p12;q21) involving IGK::BCL2
• t(18;22)(q21;q11.2) involving IGL::BCL2 1

These variants are less common but functionally similar to the classic t(14;18) translocation.

Pitfalls in Detection

• False negatives can occur with conventional techniques, with FISH and PCR improving detection rates 5
• Some follicular lymphomas (approximately 10-15%) may lack the t(14;18) but may have other genetic alterations such as BCL6 rearrangements 1
• Interpretation should always be integrated with histological findings and immunophenotype 2