What is the recommended imaging and staging workup for suspected gastrointestinal lymphoma, including CT, PET/CT, endoscopic ultrasound, MRI, and bone‑marrow biopsy?

Imaging and Staging Workup for Suspected Gastrointestinal Lymphoma

For suspected gastrointestinal lymphoma, PET-CT is the gold standard imaging modality for FDG-avid histologies (most GI lymphomas including DLBCL), while contrast-enhanced CT is preferred for variably FDG-avid marginal zone lymphomas; endoscopic ultrasound is mandatory for gastric lymphomas to assess wall infiltration depth, and bone marrow biopsy is required for marginal zone and splenic marginal zone lymphomas but can be omitted in DLBCL if PET-CT is negative. 1, 2

Primary Imaging Strategy

PET-CT (First-Line for Most GI Lymphomas)

• Use PET-CT as the primary staging modality for all FDG-avid lymphomas, which includes most GI lymphomas except marginal zone lymphomas 1
• PET-CT changes stage in 10-30% of patients (typically upstaging) and is critical as baseline measurement before therapy to enable accurate response assessment 1
• Include contrast-enhanced CT component when:
  • Distinguishing bowel from lymphadenopathy is necessary
  • Central/mediastinal vessel compression or thrombosis is present
  • Radiation planning is anticipated 1

CT Alone (For Marginal Zone Lymphomas)

• Use contrast-enhanced CT for marginal zone lymphomas, which show variable FDG avidity 1, 2
• Complete chest and abdominal CT (or MRI) is mandatory 2
• Chest x-ray is no longer required as it is less accurate than CT 1

Site-Specific Imaging Requirements

Gastric Lymphoma (Most Common GI Site)

Endoscopic ultrasound (EUS) is essential for gastric marginal zone lymphoma to:

• Define gastric wall infiltration depth (critical for Paris staging system)
• Assess perigastric lymph node involvement
• Predict response to H. pylori eradication therapy 2, 3

Endoscopy protocol:

• Perform esophagogastroduodenoscopy (EGD) with multiple biopsies from each gastric region, duodenum, and gastroesophageal junction 2
• Second endoscopy with extensive mapping may be mandatory since lymphomas can be multifocal or show mixed small/large cell components 3

Small Bowel Lymphoma

• CT or PET-CT depending on histology
• Consider enteroscopy for enteropathy-associated T-cell lymphoma 3
• Important caveat: Intestinal biopsies are frequently negative in marginal zone lymphoma; if clinical suspicion is high, consider peripheral lymph node biopsy or surgical resection of hypermetabolic nodes 4

Additional Mandatory Staging Components

Bone Marrow Biopsy

Selective approach based on histology:

• Mandatory for nodal marginal zone lymphoma and splenic marginal zone lymphoma 2
• Highly recommended for extranodal marginal zone lymphoma, particularly non-gastric sites 2
• Can be omitted in DLBCL if PET-CT is negative and identifying discordant histology is not important for management 1
• Can be omitted in Hodgkin lymphoma if PET-CT is performed 1

Extended Staging for Marginal Zone Lymphoma

Given the multifocal nature of marginal zone lymphoma (25% of gastric, 46% of extragastric cases show multiorgan involvement 5), perform:

• Imaging of orbits and salivary glands (CT or MRI) 2
• Routine EGD even for non-GI marginal zone lymphoma, especially in females and those with lung, upper airway, or salivary gland involvement 2
• Colonoscopy with multiple biopsies 5
• Otorhinolaryngologic assessment 5

Laboratory Workup

Mandatory tests include:

• Complete blood count with differential (flow cytometry of peripheral blood mandatory for nodal and splenic marginal zone lymphoma) 2
• LDH and β2-microglobulin
• Protein electrophoresis and serum/urine immunofixation
• HCV serology (if positive: HCV-RNA PCR, genotyping, cryoglobulins) 2
• HBV markers and HIV serology 2

Critical Pitfalls to Avoid

1. Do not rely on endoscopic biopsies alone for marginal zone lymphoma—they are frequently negative despite disease presence 4
2. Do not skip EUS in gastric lymphoma—wall infiltration depth predicts H. pylori eradication response 2, 3
3. Do not assume localized disease in marginal zone lymphoma—extensive staging reveals multifocal involvement in 25-46% of cases 5
4. Do not use PET-CT alone for marginal zone lymphoma—sensitivity is lower than for other lymphomas; contrast-enhanced CT is preferred 1, 2
5. Do not perform routine bone marrow biopsy in DLBCL if PET-CT is available and negative 1

Emerging Considerations

While traditional teaching suggests limited utility of PET in marginal zone lymphoma, modern PET-CT equipment with increased sensitivity may be useful when only localized treatment is planned or when transformation to high-grade histology is suspected 2. Recent data on PET/MRI with CXCR4-targeting tracers shows promise (97% accuracy) but remains investigational 6.