Small bowel lymphoma is the most common primary malignant tumor of the small intestine, accounting for approximately 20-30% of all gastrointestinal lymphomas. Non-Hodgkin lymphoma (NHL) is the most common type, with diffuse large B-cell lymphoma (DLBCL) and MALT lymphoma being the most prevalent subtypes. It most commonly occurs in the ileum because Peyer's patches are the region with the highest lymphoid tissue concentration. Immunosuppression (HIV, organ transplant), celiac disease (enteropathy-associated T-cell lymphoma — EATL), and Crohn's disease are risk factors. Clinically, it may present with abdominal pain, weight loss, obstruction, intussusception, or perforation. CT enterography is the primary diagnostic modality; aneurysmal dilatation, homogeneous wall thickening, and sandwich sign are characteristic findings. PET-CT is used for staging and treatment response assessment.
Age Range
35-75
Peak Age
55
Gender
Male predominant
Prevalence
Uncommon
Small bowel lymphoma originates from lymphoid tissue in the bowel wall (particularly from Peyer's patches and lymphoid aggregates in the lamina propria). In B-cell lymphomas, clonal B lymphocyte proliferation shows transmural infiltration — tumor cells infiltrate all layers from submucosa to serosa but characteristically destroy the muscularis propria. Therefore, despite bowel wall thickening, aneurysmal dilatation develops instead of luminal narrowing — wall tone is lost due to muscularis propria infiltration and destruction, and peristaltic activity decreases. On CT, this finding is termed 'aneurysmal dilatation' and is highly characteristic of lymphoma. Homogeneous wall thickening results from uniform cellular infiltration by the tumor — lymphoma cells spread evenly without vascular stroma and necrosis, so the enhancement pattern is homogeneous (unlike the heterogeneous pattern in adenocarcinoma or GIST). The 'sandwich sign' describes mesenteric lymph nodes encasing mesenteric vessels from both sides — lymphomatous nodes envelop rather than invade vessels due to their soft, pliable nature. In immunosuppression (HIV, post-transplant), EBV-associated lymphoma development is common. In celiac disease, chronic mucosal inflammation and intraepithelial lymphocyte activation predispose to EATL development.
The combination of luminal expansion despite wall thickening (aneurysmal dilatation) and lymphadenopathy encasing mesenteric vessels (sandwich sign) is pathognomonic for small bowel lymphoma. This combination helps distinguish from adenocarcinoma (luminal narrowing) and GIST (eccentric growth, necrosis).
Prominent wall thickening in the affected small bowel segment with luminal expansion rather than narrowing — 'aneurysmal dilatation.' Lumen diameter is dilated beyond normal caliber without proximal obstruction findings. This finding is specific to lymphoma, in contrast to the luminal narrowing of adenocarcinoma. Results from loss of tone of the muscularis propria due to lymphomatous infiltration.
Report Sentence
Segmental wall thickening with luminal expansion (aneurysmal dilatation) in the small bowel is consistent with lymphoma.
Sandwich sign — enlarged mesenteric lymph nodes encasing mesenteric arteries and veins from both sides creating a 'sandwich' appearance. Lymphadenopathy is homogeneous, soft tissue density, usually conglomerate. Mesenteric vessels remain patent because lymphoma encases rather than invades vessels. This finding is highly characteristic of lymphoma.
Report Sentence
Conglomerate lymphadenopathy encasing mesenteric vessels from both sides (sandwich sign) is consistent with lymphoma.
Segmental, homogeneous bowel wall thickening — usually >1 cm. Thickening may be concentric (symmetric) or eccentric (asymmetric). Enhancement is homogeneous and mild to moderate — necrosis and calcification are rare. Length of wall thickening varies from several cm to 20 cm. Mucosal folds are thickened but preserved.
Report Sentence
Segmental, homogeneously enhancing wall thickening in the small bowel is consistent with lymphoma.
Intense FDG uptake in the affected small bowel segment on PET-CT (SUVmax typically >10). Intense FDG uptake is also seen in mesenteric lymphadenopathy. PET-CT has a critical role in staging (other nodal/extranodal involvement sites) and treatment response assessment. Deauville score is used to assess response to chemotherapy.
Report Sentence
Segmental wall thickening with intense FDG uptake in the small bowel and accompanying FDG-avid mesenteric lymphadenopathy are consistent with lymphoma.
Prominent diffusion restriction on DWI — increased signal in highly cellular lymphoma tissue. ADC values are low (typically <1.0 × 10⁻³ mm²/s). Diffusion restriction reflects high cellularity of lymphoma and is used in treatment response monitoring — ADC values increase after successful treatment.
Report Sentence
Diffusion restriction with low ADC values in the segment showing wall thickening in the small bowel is consistent with lymphoma.
Simultaneous involvement of multiple segments of the small bowel — multifocal or diffuse lymphoma. Involvement areas may be separate (skip lesions) or continuous (diffuse). Each involvement area shows homogeneous wall thickening. Multifocal involvement is important for diagnosis because adenocarcinoma is usually unifocal.
Report Sentence
Simultaneous homogeneous wall thickening in multiple small bowel segments is consistent with multifocal lymphoma.
Criteria
Most common primary intestinal lymphoma subtype — aggressive clinical course
Distinct Features
Large mass or prominent wall thickening, may show heterogeneous enhancement, rapid growth, high FDG uptake (SUVmax >15)
Criteria
Low-grade B-cell lymphoma — indolent course
Distinct Features
Less prominent wall thickening, homogeneous enhancement, slow growth, low-moderate FDG uptake, may be multifocal
Criteria
T-cell lymphoma developing in the setting of celiac disease — jejunal localization
Distinct Features
Jejunum predominant, multifocal ulcerative lesions, high perforation risk, celiac disease history, poor prognosis
Criteria
Multiple polypoid lesions in small bowel and colon — lymphomatous polyposis pattern
Distinct Features
Multiple polypoid masses, involvement of all GI tract segments, multiple submucosal nodules on CT, aggressive course
Distinguishing Feature
Adenocarcinoma shows annular wall thickening with luminal NARROWING (apple core sign); lymphoma shows luminal EXPANSION (aneurysmal dilatation). Adenocarcinoma enhances heterogeneously while lymphoma is homogeneous.
Distinguishing Feature
GIST shows exophytic growth and is usually unifocal; lymphoma shows submucosal infiltrative growth. Central necrosis and heterogeneous enhancement are common in GIST; homogeneous enhancement is characteristic of lymphoma.
Distinguishing Feature
Crohn's disease shows skip lesions, fistula/abscess, comb sign, and 'fat wrapping.' Fistula and abscess are absent in lymphoma. Crohn usually affects the terminal ileum while lymphoma can occur in any small bowel segment.
Distinguishing Feature
Metastasis is usually multiple, heterogeneously enhancing nodules or masses; known primary malignancy history is present. Homogeneous enhancement and aneurysmal dilatation are distinguishing in lymphoma.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
specialist-referralSmall bowel lymphoma requires histopathological diagnosis by biopsy — excisional biopsy or endoscopic biopsy is preferred. Treatment varies by subtype: R-CHOP chemotherapy for DLBCL; antibiotics and/or radiotherapy for MALT; intensive chemotherapy for EATL. PET-CT is used for staging and treatment response assessment. Complications (obstruction, perforation, bleeding) may require emergency surgery.
Small bowel lymphoma is treated with chemotherapy. Surgery may be needed in perforated or obstructive cases. PET-CT is critical for staging and treatment response assessment. Immunosuppression and celiac disease are risk factors.