Non-Hodgkin Lymphoma

Detailed Overview

NHL encompasses over 60 distinct subtypes with widely varying clinical courses, from indolent (e.g., Follicular Lymphoma) to highly aggressive (e.g., Diffuse Large B-Cell Lymphoma, Burkitt Lymphoma). The pathogenesis involves specific chromosomal translocations disrupting oncogenes or tumor suppressor genes. Unlike Hodgkin lymphoma, NHL tends to spread non-contiguously and often presents with advanced-stage, extranodal disease including bone marrow, GI tract, or CNS involvement.

Epidemiology & Demographics

The most common hematologic malignancy. Incidence is roughly 19 per 100,000 annually in the US. Median age at diagnosis is 67 years. Diffuse Large B-Cell Lymphoma (DLBCL) is the most common subtype (~30%).

Etiological Mechanism

Most cases are idiopathic. Specific viral infections (EBV, HTLV-1, HIV, HCV), bacterial infections (H. pylori for MALT lymphoma), and autoimmune conditions or immunosuppression strongly predispose to its development.

Primary Causes

Acquired genetic damage to lymphocytes, notably translocations linking oncogenes to immunoglobulin promoters (e.g., t(14;18) BCL2 in Follicular Lymphoma, t(8;14) MYC in Burkitt Lymphoma).

• Immunosuppression: HIV/AIDS or post-solid organ transplant significantly increases risk (Primary CNS lymphoma, PTLD).
• Autoimmune Diseases: Sjögren's syndrome, Hashimoto thyroiditis, and Celiac disease.
• Infections: Epstein-Barr virus (Burkitt), Helicobacter pylori (Gastric MALT lymphoma).

Genetic mutations halt lymphocyte differentiation or inhibit apoptosis. For instance, in Follicular Lymphoma, the t(14;18) translocation places the BCL-2 anti-apoptotic gene under the control of the active IgH promoter, leading to BCL-2 overexpression. These immortalized cells proliferate and replace normal lymph node architecture. Extranodal spread occurs via hematogenous or lymphatic routes. Aggressive subtypes have high proliferation fractions (Ki-67 >80%) rapidly expanding tumor mass.

Characteristic Clinical Presentation

• Painless Lymphadenopathy: Firm, rubbery, enlarged lymph nodes, commonly cervical, axillary, or inguinal.
• B Symptoms: Fever (>38 C), drenching night sweats, and unintentional weight loss (>10% of body weight in 6 months).
• Abdominal pain or fullness: Due to massive splenomegaly or bulky retroperitoneal adenopathy compressing adjacent structures.
• Dyspnea: Secondary to large mediastinal masses compressing the airway or superior vena cava.

Physical Examination Signs

• Palpable enlarged, non-tender lymph nodes.
• Hepatosplenomegaly on abdominal exam.
• Superior Vena Cava (SVC) syndrome signs: facial plethora, jugular venous distention.

• Tumor Lysis Syndrome: Rapid destruction of cancer cells releasing intracellular contents, causing severe electrolyte derangements and acute renal failure.
• Cytopenias: Anemia, neutropenia, and thrombocytopenia due to bone marrow infiltration.
• Bowel obstruction or perforation: If lymphoma heavily involves the GI tract (common in Burkitt or DLBCL).

Diagnostic Criteria & Guidelines

Requires excisional lymph node biopsy or adequate core needle biopsy demonstrating architectural effacement by malignant lymphocytes. Immunohistochemistry (IHC) or flow cytometry is mandatory to define the immunophenotype (e.g., CD20+ for B-cell).

Differential Diagnosis

• Hodgkin Lymphoma
• Infectious Mononucleosis
• Tuberculosis (Tuberculous lymphadenitis)
• Metastatic Carcinoma

Laboratory Tests & Biomarkers

• Lactate Dehydrogenase (LDH): Often significantly elevated; a key prognostic marker for tumor burden and turnover.
• Comprehensive Metabolic Panel (CMP): Elevated uric acid, potassium, and phosphorus if Tumor Lysis Syndrome is present.
• Excisional Biopsy IHC: B-cell markers (CD19, CD20) or T-cell markers (CD3). Specifics like BCL2, BCL6, MYC for subtyping.

Imaging Modalities & Findings

• PET/CT Skull base to mid-thigh:

• Ann Arbor Stage I
  Involvement of a single lymph node region or localized involvement of a single extralymphatic organ.
• Ann Arbor Stage II
  Involvement of two or more lymph node regions on the same side of the diaphragm.
• Ann Arbor Stage IV
  Diffuse or disseminated involvement of one or more extralymphatic organs (e.g., bone marrow, liver).

Second-Line & Adjunctive Therapy

For relapsed/refractory DLBCL: Salvage chemotherapy (e.g., R-ICE) followed by Autologous Stem Cell Transplant if chemosensitive. CAR-T cell therapy (e.g., Axicabtagene ciloleucel) is increasingly used for early relapse or transplant-ineligible patients.

Surgical & Procedural Management

Surgery is strictly diagnostic (excisional biopsy). Seldom therapeutic except for resecting localized GI lymphomas (e.g., to prevent perforation) or splenectomy for massive symptomatic splenomegaly.

Recommended Lifestyle Changes

• Strict adherence to food safety and hygiene to prevent infections during neutropenic periods.
• Maintain moderate physical activity to mitigate chemotherapy-induced fatigue.

Patient Counseling & Advice

Discuss fertility preservation before starting chemo. Warn about alopecia, neuropathy (vincristine), and risk of cardiotoxicity (doxorubicin). Inform them of the risk of secondary malignancies down the line.

Follow-Up & Monitoring Schedule

Post-treatment: Clinical exam and basic labs every 3-6 months for 5 years. Routine surveillance PET/CT is generally NOT recommended due to false positives, unless clinical suspicion of relapse arises.

Preventive Strategies

No specific prevention. Treatment of underlying causes where applicable (e.g., eradicating H. pylori can cure early-stage gastric MALT lymphoma; treating HIV reduces risk).

Highly variable by subtype and IPI (International Prognostic Index) score. DLBCL is curable in ~60-70% of cases. Follicular lymphoma is considered incurable but has a median survival of >15 years.