Colorectal lymphoma encompasses primary or secondary non-Hodgkin lymphomas (NHL) of the gastrointestinal system. Approximately 10-20% of GI lymphomas occur in the colon or rectum, with the cecum being the most commonly involved site. Primary colorectal lymphoma is most frequently diffuse large B-cell lymphoma (DLBCL) and MALT lymphoma. Aneurysmal dilatation (luminal widening) is a characteristic finding of colorectal lymphoma and differs from the stricture formation of adenocarcinoma — because lymphoma infiltrates the muscularis propria, destroying the autonomic nerve plexus and causing loss of peristaltic function. When evaluated together with homogeneous wall thickening, minimal obstruction, and peritoneal/mesenteric lymphadenopathy, the diagnosis is strengthened. The risk of colorectal lymphoma is markedly increased in immunosuppressed patients (HIV, post-transplant).
Age Range
40-75
Peak Age
60
Gender
Male predominant
Prevalence
Uncommon
Colorectal lymphoma originates from mucosa-associated lymphoid tissue (MALT) or lymphoid follicles within the bowel wall. Diffuse lymphoid infiltration in the colon wall involves all layers and infiltrates the muscularis propria. Lymphomatous infiltration of the autonomic nerve plexus (Auerbach and Meissner plexuses) disrupts peristaltic function, producing aneurysmal dilatation (luminal widening) — this is the fundamental difference from adenocarcinoma's stricture formation through desmoplastic reaction. Homogeneous infiltration of lymphoid cells produces smooth, concentric wall thickening; because desmoplastic reaction and fibrosis are minimal, obstruction is rare. Homogeneous, low-to-moderate enhancement on CT reflects the uniform cellular architecture of lymphoid tissue — necrosis may be seen in high-grade types but is not as prevalent as in adenocarcinoma. High FDG uptake on PET results from the high metabolic activity of lymphoid cells.
Lymphoma infiltrates the bowel wall and destroys the myenteric plexus (Auerbach plexus), causing loss of peristaltic function and segmental bowel dilatation (aneurysmal dilatation). This finding fundamentally distinguishes it from adenocarcinoma's stricture formation — adenocarcinoma narrows the lumen through desmoplastic reaction, while lymphoma widens it.
Circumferential, homogeneous, low-to-moderate enhancing wall thickening of the colon/rectum in portal venous phase. Wall thickness is typically 1-3 cm. The lumen is usually preserved or widened (aneurysmal dilatation) — obstruction and proximal dilatation are rare. The thickened wall is homogeneous without significant necrosis or ulceration. Infiltration of surrounding fat tissue may be minimal.
Report Sentence
Circumferential homogeneous wall thickening with aneurysmal dilatation in the colon/rectum is observed, and colorectal lymphoma should be considered as the leading diagnosis.
Mesenteric lymphadenopathy frequently accompanies colorectal lymphoma. Enlarged lymph nodes surround mesenteric vessels creating the 'sandwich sign' — superior and inferior mesenteric artery/vein branches appear trapped between conglomerate lymph nodes. LAP is usually homogeneous, low-to-moderate density with smooth margins. Necrotic lymph nodes may be seen in high-grade lymphoma.
Report Sentence
Conglomerate mesenteric lymphadenopathy creating 'sandwich sign' surrounding mesenteric vessels is observed, highly consistent with lymphoma.
Thickened bowel wall demonstrates low-to-moderate enhancement in the arterial phase. The neovascularity of lymphoid tissue is less than adenocarcinoma or GIST. Enhancement is homogeneous without significant heterogeneity or necrosis (except high-grade lymphomas). Target sign may be visible — mucosal hyperemic enhancement, submucosal edematous hypodense line, and serosal enhancement layers.
Report Sentence
Homogeneous low-to-moderate enhancement of the thickened bowel wall in arterial phase is observed, consistent with lymphoproliferative disease.
Colorectal lymphoma demonstrates prominent FDG uptake on FDG PET-CT. Very high uptake (SUVmax typically >10-15) is seen in DLBCL and Burkitt lymphoma. Uptake may be lower in MALT lymphoma (SUVmax 3-8). PET-CT plays a critical role in determining disease extent (staging) and evaluating treatment response (Deauville criteria). FDG uptake in mesenteric and retroperitoneal LAP confirms systemic disease.
Report Sentence
Intense FDG uptake in colon/rectum wall thickening and accompanying mesenteric lymphadenopathy on PET-CT is observed, highly consistent with lymphoma.
The thickened bowel wall shows intermediate-to-high hyperintense signal on T2-weighted images. The signal is homogeneous, reflecting the uniform cellular architecture of lymphoid tissue. Areas of necrosis may be seen in high-grade lymphoma showing marked T2 hyperintensity. MRI is superior to CT for local staging and evaluating relationship with surrounding structures, especially in rectal lymphoma.
Report Sentence
Homogeneous hyperintense circumferential wall thickening on T2-weighted images is observed, consistent with lymphoproliferative infiltration.
Marked diffusion restriction in the thickened bowel wall on DWI — hyperintense signal at high b-value, low signal on ADC map (low ADC values). The high cellularity of lymphoma produces marked diffusion restriction, and this finding may more reliably distinguish lymphoma from adenocarcinoma. ADC values are typically in the <0.8-1.0 × 10⁻³ mm²/s range.
Report Sentence
Marked diffusion restriction with low ADC values in the bowel wall thickening on DWI is observed, consistent with highly cellular lymphoma.
Criteria
Most common colorectal lymphoma subtype (50-60%). Rapid growth, aggressive course. Tendency to form large masses, may contain necrosis. Very high FDG uptake on PET-CT (SUVmax >10-15).
Distinct Features
Large (>5 cm) focal mass or segmental wall thickening. Necrosis and ulceration more frequent. Risk of perforation (5-10%). Very marked diffusion restriction on DWI. High response rate to R-CHOP chemotherapy.
Criteria
Low-grade B-cell lymphoma. Slow growth, indolent course. Higher probability of localized disease. Low-to-moderate FDG uptake on PET-CT (SUVmax 3-8).
Distinct Features
Thinner and more homogeneous wall thickening. Necrosis is rare. Risk of high-grade transformation (Richter transformation). Local treatment (surgery/radiotherapy) may be sufficient. Colonic MALT may develop in the setting of chronic inflammation.
Criteria
Presents as multiple polypoid lesions — 'lymphomatous polyposis' pattern. May mimic familial adenomatous polyposis (FAP). Older age, male predominance.
Distinct Features
Numerous (>50) polypoid lesions distributed throughout the colon. Each polyp shows low-to-moderate enhancement. Mesenteric LAP accompanies. Waldeyer ring and small bowel involvement is common. Poor prognosis; may respond to ibrutinib-based treatment regimens.
Criteria
Very aggressive high-grade B-cell lymphoma. More common in children and young adults. Ileocecal region is the most commonly involved site. Ki-67 nearly 100%. May be HIV-associated.
Distinct Features
Rapidly growing large mass with marked necrosis. Highest FDG uptake on PET-CT (SUVmax >15-20). Very low ADC values on DWI. Requires urgent chemotherapy (tumor lysis syndrome risk). Intussusception may be seen in colorectal Burkitt lymphoma.
Distinguishing Feature
Adenocarcinoma forms stricture and causes proximal obstruction (apple-core defect); lymphoma shows aneurysmal dilatation with rare obstruction. Adenocarcinoma demonstrates heterogeneous enhancement and mucosal irregularity; lymphoma shows homogeneous thickening.
Distinguishing Feature
GIST grows as exophytic mass with heterogeneous enhancement; lymphoma forms circumferential wall thickening. GIST is solitary; lymphoma may be multifocal with accompanying LAP. c-KIT positivity in GIST is diagnostic.
Distinguishing Feature
Crohn disease shows skip lesions, fistulas, strictures, and proliferative mesenteric fat (creeping fat); lymphoma demonstrates more uniform thickening with LAP. Wall thickening in Crohn is usually <1.5 cm; in lymphoma may be >1.5-3 cm.
Distinguishing Feature
Metastasis usually presents with known primary malignancy as focal mass; lymphoma shows circumferential thickening. Metastasis usually does not show mesenteric LAP (peritoneal implants more typical); bulky LAP is characteristic in lymphoma.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
specialist-referralColonoscopic or surgical biopsy is required for colorectal lymphoma diagnosis — histopathological subtype determination is mandatory for treatment planning. R-CHOP chemotherapy is standard treatment for DLBCL; surgery is usually not needed (chemotherapy response is very high). Local treatment may suffice for MALT lymphoma. Urgent chemotherapy is needed for Burkitt lymphoma (tumor lysis syndrome prophylaxis mandatory). PET-CT is standard for staging and treatment response evaluation (Deauville criteria). Complications: perforation (5-10%, especially during chemotherapy), bleeding, intussusception. Dawson criteria are used for primary colorectal lymphoma definition.
Responds well to chemotherapy; surgery is usually not needed. Diagnosis is made by biopsy. PET-CT is used for staging and treatment response assessment.