Non-Hodgkin Lymphoma: High-Yield Malignancies & Chromosomal Translocations
Non-Hodgkin Lymphoma (NHL) represents a diverse group of malignancies originating primarily within lymphoid tissues, most commonly from neoplastic B-cells (around 85%) and less frequently from T-cells or NK-cells. In contrast to Hodgkin Lymphoma, NHL exhibits non-contiguous hematogenous spread, involves extra-nodal sites early (such as the GI tract, skin, and CNS), and the tumor mass consists almost entirely of neoplastic lymphoid cells rather than a reactive inflammatory background.
1. Pathophysiology and Clinical Differentiation
NHL typically presents in older adults (median age over 60, with specific notable childhood exceptions like Burkitt lymphoma) and is clinically distinguished from Hodgkin lymphoma by several high-yield parameters:
- Nodal Spread: Diffuse, unpredictable, and non-contiguous, meaning it can skip distant anatomical node chains without order.
- Extra-nodal Involvement: Highly common, frequently manifesting as primary gastrointestinal tumors (such as MALT lymphoma), skin lesions, or central nervous system masses.
- Systemic Manifestations: Systemic B-symptoms (fever, drenching night sweats, weight loss) are present but are typically associated primarily with high-grade, aggressive histological subtypes.
Classic “starry sky” histological appearance: a dense sea of dark, rapidly proliferating neoplastic B-cells interspersed with light, lipid-laden tingible body macrophages clearing away apoptotic debris.
2. High-Yield B-Cell Subtype Breakdown
The vast majority of board questions focus on specific, highly conserved cytogenetic translocations that define individual B-cell NHL subtypes:
| NHL Subtype | Cytogenetics & Molecular Mechanism | High-Yield Clinical Features |
|---|---|---|
| Diffuse Large B-Cell Lymphoma (DLBCL) | • Alterations or mutations in the BCL6 gene on chromosome 3 are common. • Can arise de novo or evolve secondarily from low-grade lymphomas (such as Follicular Lymphoma or CLL/Richter Transformation). |
Most common NHL subtype in adults. Highly aggressive, fast-growing mass presenting with severe B-symptoms. Requires immediate, intensive R-CHOP chemotherapy regimens. |
| Follicular Lymphoma | • t(14;18) translocation: Fuses the heavy-chain IgG locus on chromosome 14 with the BCL2 gene on chromosome 18. • Overexpression of BCL2 stabilizes mitochondrial membranes, completely blocking normal apoptosis within the germinal center. |
Indolent, long-standing course presenting as painless, waxing-and-waning generalized lymphadenopathy. Difficult to fully cure, but manageable with low-intensity therapies over the years. |
| Burkitt Lymphoma | • t(8;14) translocation: Moves the c-myc oncogene on chromosome 8 to the heavy-chain IgG locus on chromosome 14. • c-myc acts as a potent transcriptional activator, triggering extreme, uninhibited cell proliferation. |
Highly associated with EBV. Presents in children as an endemic African jaw mass or a **sporadic abdominal mass**. Displays the pathognomonic starry-sky histology. Extremely high mitotic index. |
| Mantle Cell Lymphoma | • t(11;14) translocation: Fuses the Cyclin D1 gene on chromosome 11 with the heavy-chain IgG locus on chromosome 14. • Overexpression of Cyclin D1 forces cells aggressively past the G1/S cell-cycle checkpoint by phosphorylating the Rb protein. |
Presents predominantly in older males with advanced-stage disease, including hepatosplenomegaly, generalized lymphadenopathy, and GI tract infiltration. Clinically aggressive with a poor prognosis. |
| Marginal Zone / MALT Lymphoma | • Frequently driven by a t(11;18) translocation. • Arises directly within mucosal sites that have undergone extensive, chronic inflammatory hyperplasia. |
Strongly associated with chronic inflammatory states like **Helicobacter pylori gastritis**, Sjögren syndrome, or Hashimoto thyroiditis. Early-stage gastric MALTomas often **regress completely following H. pylori antibiotic eradication**. |
3. T-Cell / NK-Cell Subtypes of Note
Though less common, these variants carry high-yield, unique clinical presentations that appear frequently on exams:
- Adult T-Cell Leukemia/Lymphoma (ATLL): Caused explicitly by HTLV-1 infection. Classically presents with cutaneous lesions, hepatosplenomegaly, generalized lymphadenopathy, and **lytic bone lesions with hypercalcemia** (must be differentiated from Multiple Myeloma by the presence of a skin rash and neoplastic T-cells displaying characteristic “cloverleaf” or “flower” nuclei).
- Mycosis Fungoides / Sézary Syndrome: A primary cutaneous T-cell lymphoma (neoplastic CD4+ helper T-cells) infiltrating the epidermis, creating characteristic microabscesses (Pautrier microabscesses). When it breaks out into the peripheral circulation, it causes erythroderma, generalized lymphadenopathy, and circulating malignant T-cells with highly folded, **cerebriform nuclei** (Sézary Syndrome).