Features of splenic and hepatic involvement
The spleen is involved frequently, but imaging patterns depend heavily on the tumor type. In Hodgkin lymphoma (HL), involvement is typically microscopic and diffuse, making visualization on tomograms extremely difficult. It is important to remember that splenomegaly in HL is an unreliable criterion. About 33% of enlarged spleens contain no tumor, and 33% of normal-sized organs prove to be infiltrated according to histology.
In non-Hodgkin lymphoma (NHL), conversely, splenomegaly serves as a fairly reliable sign of the disease (size greater than 13 cm on CT). Focal changes occur in 10–25% of cases. The introduction of FDG PET/CT has radically changed the approach to staging, as the high accuracy of the method allowed for the abandonment of traumatic staging laparotomies with splenectomy.
As for the liver, a specific sign (especially in pediatric practice) is periportal infiltration—the appearance of low-density tissue cuffing the portal vein. True primary hepatic lymphomas are extremely rare and radiologically mimic hepatocellular carcinoma.
Gastrointestinal tract as a preferred extranodal site
The GI tract accounts for up to 45% of all extranodal manifestations. The diagnosis of primary gastrointestinal lymphoma is established according to strict criteria: absence of enlarged peripheral and mediastinal lymph nodes, intact liver and spleen, and normal white blood cell count. Only local enlargement of regional lymph nodes is permitted. Staging is performed using the modified Lugano system (Lugano).
The stomach is most commonly affected (about 50% of GI lesions). The tumor grows from the submucosal layer (lamina propria), forming multiple nodules, large polypoid masses, or causing total diffuse wall thickening that appears identical to linitis plastica on CT. Most tumors show high radiotracer uptake on PET.
In the small intestine (35%), involvement is concentrated predominantly in the terminal ileum. Tumor growth through the wall causes destruction of autonomic plexuses, leading to a specific imaging sign: aneurysmal dilatation of the affected segments. In children, polypoid forms in the ileocecal region are the most frequent cause of intussusception.
Pancreatic and renal involvement
Pancreatic lymphoma (both primary and secondary in NHL) usually presents as a solitary mass in the head, which is difficult to distinguish from primary adenocarcinoma on scans. However, unlike carcinoma, lymphoma typically lacks calcification, necrosis, and vascular effacement.
The kidneys are involved predominantly in advanced stages of high-grade NHL, but renal function is usually unaffected. CT most commonly reveals multiple bilateral nodules (in 60% of cases). They are characterized by the "density reversal pattern": before contrast administration, tumor masses appear denser than the renal parenchyma, and after contrast enhancement, they become less dense compared to it. Notably, in more than half of renal lymphomatosis cases, retroperitoneal lymph nodes remain completely normal in size.
Briefly: answers to topical questions
What CT signs help differentiate pancreatic lymphoma from adenocarcinoma?
Pancreatic lymphoma can be differentiated from adenocarcinoma on CT by features that are uncommon in lymphoma.
| Sign | Lymphoma | Adenocarcinoma |
|---|---|---|
| Calcification | Rarely | Frequent |
| Necrosis | Rarely | Frequent |
| Vascular effacement (vascular effacement) | Rarely | Frequent |
Otherwise, lymphoma usually presents as a solitary mass that is visually indistinguishable from primary adenocarcinoma.
What hepatic parenchymal involvement patterns are seen in lymphomas on CT?
CT identifies several patterns of hepatic parenchymal involvement in lymphomas.
- Multiple lesions—defined as poorly defined low-density areas.
- Periportal infiltration—visualized as low-density tissue spreading from the porta hepatis and cuffing the portal vein.
- Solitary lesion—a single mass that, in primary lymphoma, is radiologically indistinguishable from hepatocellular carcinoma.
- Diffuse involvement—has non-specific imaging features.
What radiological variants of renal involvement are distinguished in lymphoma?
CT identifies two main radiological variants of renal involvement in lymphoma.
- Multiple masses—the most frequent pattern (60%), often bilateral. It is characterized by the "density reversal pattern" (density reversal pattern), in which masses are denser than the surrounding parenchyma before contrast and less dense after it.
- Solitary mass—occurs in 5–15% of cases and may be visually indistinguishable from renal cell carcinoma.
An important sign is the absence of concomitant retroperitoneal lymphadenopathy in more than half of the cases.
What stages are distinguished in the modified Lugano classification for GI lymphomas?
The modified Lugano staging system (Lugano) for primary gastrointestinal lymphomas distinguishes two main stages.
- Stage I—tumor involvement is restricted to the bowel wall only.
- Stage II—involvement of draining lymph nodes or extension to adjacent organs is observed.
This classification is used to assess the localization and extent of primary GI lymphomas, which most frequently affect the stomach, small intestine, and colon.
To memorize the frequency of GI segment involvement, use the descending rule: S-S-C — Stomach (50%), Small intestine (35%), Colon (15%).
Class and exam questions
Is splenomegaly an accurate imaging sign of splenic involvement in lymphomas?
In non-Hodgkin lymphomas, yes. In Hodgkin lymphoma, this is an unreliable marker: a third of patients with an enlarged spleen have no tumor, and a third with a normal organ size have infiltration.
What is the "density reversal pattern" in renal involvement?
This is a characteristic CT sign of multiple lymphomatous nodules: on unenhanced scans, they appear denser than healthy parenchyma, and after contrast administration, they become less dense.
Why does aneurysmal dilatation occur in small bowel lymphoma?
This occurs due to progressive tumor spread through the muscularis propria and infiltration of the autonomic nerve plexus of the bowel wall.
What else to study on this topic
- Endoscopic ultrasound in the staging of gastric MALT lymphoma
- Specific forms of intestinal lymphoma: heavy chain disease (IPSID)
- Differential diagnosis of lymphoma and pancreatic adenocarcinoma on CT
- Radiological appearance of AIDS-related lymphoma (ARL) of the anorectal region
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