Lymphoma for Radiology Board Review Part 1
Review of lymphoma imaging manifestations and other high yield topics about lymphoma for radiology board exam review.
Show Notes/Study Guide:
On imaging, how can we differentiate retroperitoneal fibrosis from lymphoma?
Retroperitoneal fibrosis pulls, tethers, and constricts structures inward/medially whereas lymphoma displaces and surrounds structures by pushing them outward/laterally without constriction. On imaging, for retroperitoneal fibrosis look for medial tethering ureters with ureteral strictures and hydronephrosis as well as abdominal aortic encasement without deviation. Lymphoma pushes things outwards so look for anterior displacement of abdominal aorta and lateral deviation of ureters which may be encased by soft tissue but not strictured. On MRI, retroperitoneal fibrosis would classically be T2 dark due to the fibrotic tissue. Lymphoma on MRI would typically be T2 isointense to spleen. Both can show delayed enhancement on MRI.
What is a classic appearance for renal lymphoma?
Renal lymphoma typically presents as bilateral homogeneous hypovascular round and oval circumscribed masses within the renal parenchyma. This has been described as a ‘cannon ball appearance’. Other less common manifestations can include smooth renal enlargement and/or perinephric soft tissue infiltration. With more aggressive lymphomas you may see infiltrative renal lesions. Most cases of renal lymphoma occur with widespread systemic disease. Primary renal lymphoma is much more rare than secondary renal lymphoma from systemic disease, typically NHL. Renal lymphoma is often clinically asymptomatic.
Can you develop primary lymphoma of the urinary bladder?
No. There is no lymphoid tissue in the bladder, so lymphoma of the bladder is always secondary.
What is a typical appearance for splenic lymphoma?
Most commonly, splenic lymphoma will manifest as diffuse enlargement of the spleen (splenomegaly) without a discrete lesion/mass. This is most common for a low-grade lymphoma. On FDG PET/CT you would expect splenomegaly with uptake of FDG above that of liver. Higher grade lymphomas involving the spleen may have discrete splenic nodules that would be focally FDG avid. On CT imaging these nodules are typically hypovascular compared to the normal spleen. Look for associated lymphadenopathy elsewhere as splenic lymphoma is typically a manifestation of systemic disease.
What is the most common primary tumor of the spleen that is not lymphoma?
Splenic angiosarcoma which shows infiltrative masses with internal necrosis and hemorrhage.
What is the typical imaging appearance for testicular lymphoma?
Testicular lymphoma appearance as a homogeneous hypoechoic vascular testicular mass(es) that may be indistinguishable from a testicular seminoma. Both seminoma and testicular lymphoma appear as homogeneous testicular masses whereas other testicular tumors are classically heterogeneous. Testicular lymphoma is most commonly diffuse large B cell lymphoma and is most common in older males and is frequently bilateral and may involve the epididymis. Lymphoma is the most common testicular tumor in patients over 60 years of age. Seminomas are usually seen in younger men (around 30s).
What is the typical treatment of testicular lymphoma?
Surgery/orchiectomy.
Why?
The blood testes barrier prevents chemotherapy from reaching the testicles! So, you need to surgically remove the testicles. Beware of the follow-up FDG PET scan that shows that lymphoma throughout the torso is no longer seen but testicular activity above normal persists. Sometimes testicular lymphoma is not appreciated on a baseline FDG scan due to extensive hypermetabolic disease elsewhere, especially if both testicles are involved and appear symmetric. However, after systemic chemotherapy, all other sites resolve, and you now see the testicles that are very hypermetabolic and easier to appreciate. This is the imaging manifestation of systemic chemotherapy eradicating disease elsewhere but not in the testicles due to the blood-testes barrier. Appropriate treatment is therefore typically orchiectomy.
How can colonic adenocarcinoma and lymphoma manifest differently on imaging?
If you see colonic bowel wall thickening with obstruction, think adenocarcinoma. If you see bowel wall thickening without obstruction this could be colonic lymphoma or less likely something like fungal infection. Key is that lymphoma typically does not obstruct. For small or large bowel lymphoma can present with aneurysmal dilatation of a bowel loop without obstruction, whereas adenocarcinoma constricts and obstructs the bowel lumen. On MRI, bowel lymphoma shows T2 mass isointense to spleen with delayed enhancement.
What are the top malignant causes of intussusception?
1. Lymphoma. 2. Melanoma.
What is the significance of the small bowel target sign?
This sign is the result of bowel wall edema with associated enhancement of the luminal mucosa and the external muscularis propria that give a target appearance. If you see multiple small bowel target signs, think lymphoma or metastatic melanoma. If you see a single small bowel target sign, think GIST, primary adenocarcinoma, or an ectopic pancreatic rest. Crohn’s disease and post-radiation treatment change are also possible.
What is the typical appearance of bowel lymphoma on fluoroscopy?
On fluoroscopy, bowel lymphoma may manifest as multiple thickened folds with nodularity in a segmental or diffuse pattern. A helpful mnemonic for the fluoro “thick folds with nodularity” pattern is MAIL COW. Metastasis, Abscess, Infection, Lymphoma, Crohn’s, Other (such as lymphangiectasis), Whipple’s disease. Small bowel lymphoma is rare in the United States. Most common site for small bowel lymphoma is the ileum (most lymphoid tissue there) followed by jejunum and then duodenum. Additional signs of possible small bowel lymphoma as focal circumferential narrowing of the bowel. Note that Mantle cell lymphoma has a characteristic extremely polypoid appearance on fluoroscopy. IF you have an ileocecal mass causing intussusception lymphoma is high on the differential diagnosis.
What is benign nodular lymphoid hyperplasia in the bowel and how does this appear different than lymphoma?
Benign nodular lymphoid hyperplasia appears as scattered clusters of lymph node follicles that are all the same size. This is a reactive process seen with entities like IgA deficiency, asthma, or infections. Lymphoma has larger and more variable nodules.
What are some common risk factors for small bowel lymphoma?
Celiac disease, Crohn’s disease, AIDS, and lupus are common risk factors for small bowel lymphoma.
True or false? Hashimoto’s thyroiditis has increased risk of developing thyroid lymphoma.
True. Patients with Hashimoto thyroiditis have an approximately 75% increased risk of developing thyroid NHL in addition to increased risk of papillary and Hurthle cell neoplasms.
Is hepatic lymphoma typically primary or secondary?
Primary hepatic lymphoma is very rare. If present, hepatic lymphoma usually manifests with one or more hepatic masses that are hypoechoic on ultrasound and are hypovascular on CT/MRI. Prognosis for primary hepatic lymphoma is very poor. The imaging features of secondary hepatic lymphoma are variable and include a miliary disease pattern, infiltrative disease pattern, or mass-like presentations. For secondary hepatic disease, look for co-existing splenomegaly and lymphadenopathy. For hepatic lymphoma, Hodgkin’s disease is slightly more common than non-Hodgkin’s lymphoma.
Hepatic or splenic lymphoma can present with peliosis. What is peliosis?
Peliosis is a rare condition that manifests with multiple blood-filled cystic spaces in solid organs, most commonly the liver and spleen. Causes include lymphoma, oral contraceptive use, men on steroids, AIDS, renal transplantation.
