What are the steps to diagnose abdominal lymphoma?

Diagnosis of Abdominal Lymphoma

The gold standard for diagnosing abdominal lymphoma is an excisional lymph node biopsy or adequate tissue sampling, with core needle biopsies reserved only for difficult-to-access retroperitoneal lymph nodes. 1

Initial Clinical Assessment

• Evaluate for constitutional symptoms including fever >38°C, drenching night sweats, weight loss >10% of body weight within 6 months (B symptoms), as well as alcohol intolerance, pruritus, and fatigue 1, 2
• Perform thorough physical examination of all lymphoid regions, with special attention to the abdomen for hepatosplenomegaly and abdominal masses 1, 2
• Document performance status, as this impacts treatment decisions and prognosis 1

Laboratory Evaluation

• Complete blood count with differential to assess for cytopenias or abnormal cell populations 1, 3
• Comprehensive metabolic panel including liver and renal function tests 1, 3
• Lactate dehydrogenase (LDH) and uric acid levels as markers of tumor burden and for prognostic purposes 1, 3
• Hepatitis B and C, HIV screening (mandatory before initiating rituximab therapy) 1, 3
• Consider additional tests based on suspected lymphoma subtype:
  • Protein electrophoresis for potential paraproteinemia 1, 3
  • β2-microglobulin (important prognostic marker, especially in follicular lymphoma) 1, 3
  • Coagulation studies to assess for disseminated intravascular coagulation 3

Imaging Studies

• PET/CT scan (skull base to mid-thigh) is essential for initial staging of abdominal lymphoma 1, 2
• Diagnostic contrast-enhanced CT of neck, chest, abdomen, and pelvis if PET/CT is not immediately available 1, 2
• For suspected abdominal lymphoma, CT should focus on:
  • Retrocrural nodes (abnormal if >6mm in short axis) 4
  • Upper abdominal nodes (abnormal if >10mm) 4
  • Pelvic nodes (abnormal if >15mm) 4
  • Hepatosplenomegaly and focal lesions in liver or spleen 5
• MRI may be considered in select cases, particularly for pelvic evaluation 1, 5

Tissue Diagnosis

• Excisional lymph node biopsy is the preferred diagnostic method 1
• Core needle biopsy should only be performed when excisional biopsy is not feasible (e.g., retroperitoneal nodes) 1
• Fine-needle aspiration alone is inadequate and should be avoided 1
• Tissue should be processed for:
  • Histopathology with hematoxylin and eosin staining 1
  • Immunohistochemistry (minimum panel: CD3, CD15, CD20, CD30, CD45, CD79a, PAX5 for Hodgkin lymphoma; CD45, CD20, CD3 for diffuse large B-cell lymphoma) 1
  • Flow cytometry for immunophenotyping 3
  • Fresh frozen tissue collection for potential molecular studies 1

Bone Marrow Assessment

• Bone marrow biopsy is required for complete staging 1, 3
• May be omitted in certain circumstances:
  • If PET scan is negative or shows homogeneous bone marrow uptake 1
  • If PET scan shows multifocal (≥3) skeletal lesions, bone marrow involvement can be assumed 1
• Still recommended if cytopenias are present, regardless of PET findings 1

Additional Specialized Testing

• Lumbar puncture with cerebrospinal fluid analysis for patients with high-risk features (blastoid variant, elevated LDH, impaired performance status) or neurological symptoms 1, 3
• Gastrointestinal endoscopy for patients with suspected gastrointestinal involvement or limited stage I/II disease 1, 6
• Cardiac function evaluation (MUGA scan or echocardiogram) if anthracycline-based therapy is planned 1, 3

Staging and Risk Assessment

• Ann Arbor classification system is used for staging 1
• Document presence of bulky disease (>5-10cm, depending on lymphoma type) 1
• Calculate appropriate prognostic index based on lymphoma subtype:
  • International Prognostic Index (IPI) for diffuse large B-cell lymphoma 1
  • Follicular Lymphoma International Prognostic Index (FLIPI) for follicular lymphoma 1
  • Mantle Cell Lymphoma International Prognostic Index (MIPI) for mantle cell lymphoma 1

Common Pitfalls to Avoid

• Relying solely on fine-needle aspiration for diagnosis 1
• Initiating treatment without adequate tissue diagnosis 2
• Failing to screen for hepatitis B before rituximab therapy 1, 3
• Overlooking the need for expert hematopathology review, especially for unusual presentations 1
• Neglecting to assess cardiac function before anthracycline-based therapy 1, 3
• Misinterpreting normal or anomalous vascular structures as lymphadenopathy on imaging 4