Which non-Hodgkin lymphoma is characterized by the translocation t(14;18) and overexpression of the BCL2 gene?

Explanation

## Follicular Lymphoma and t(14;18) **Key Point:** Follicular lymphoma is defined by the t(14;18)(q32;q21) translocation, present in 85–90% of cases, which juxtaposes the BCL2 anti-apoptotic gene with the immunoglobulin heavy chain (IgH) locus. ### Molecular Pathogenesis 1. **BCL2 overexpression** → impaired apoptosis 2. **Germinal centre B-cell origin** → follicular architecture preserved 3. **Indolent growth** → slow proliferation rate 4. **Transformation risk** → 10–15% transform to DLBCL over 10 years **High-Yield:** BCL2 translocation is the defining genetic feature of follicular lymphoma. Detection by fluorescence in situ hybridization (FISH) or PCR confirms the diagnosis. ### Histopathologic Features - **Grade I (low-grade):** <5 centroblasts per high-power field (HPF) - **Grade II (intermediate):** 5–15 centroblasts per HPF - **Grade III (high-grade):** >15 centroblasts per HPF - Grade IIIA: residual follicular pattern - Grade IIIB: diffuse pattern (often treated as DLBCL) ### Clinical Characteristics | Feature | Follicular Lymphoma | |---------|---------------------| | Age of onset | 50–60 years | | Stage at diagnosis | III–IV (70% of cases) | | Prognosis | Indolent; median survival 8–10 years | | Transformation | 10–15% to DLBCL | | BCL2 status | Overexpressed (t(14;18)) | | Apoptosis | Impaired | **Clinical Pearl:** Follicular lymphoma is the second most common NHL in developed countries. Despite its indolent nature and advanced stage at diagnosis, many patients have prolonged survival with observation alone ("watch and wait" strategy). **Mnemonic:** **FL-BCL2-14** — Follicular Lymphoma, BCL2 gene, chromosome 14 (IgH). ### Distinction from Other Translocations ```mermaid flowchart TD A[B-cell Lymphoma]:::outcome --> B{Which translocation?}:::decision B -->|t(14;18)| C[Follicular Lymphoma]:::outcome B -->|t(11;14)| D[Mantle Cell Lymphoma]:::outcome B -->|t(8;14)| E[Burkitt Lymphoma]:::outcome B -->|t(3;14)| F[DLBCL with BCL6]:::outcome C --> G[BCL2 overexpression]:::action D --> H[CCND1 overexpression]:::action E --> I[MYC overexpression]:::action ```