Imaging findings in lymphoma
Diagnosis of splenic lymphoma is based on detecting structural changes in the organ parenchyma. Depending on the chosen imaging method, the following features are visualized:
- Ultrasound (US): multiple masses are identified in the splenic tissue. They have an irregular shape, heterogeneous structure, and areas with reduced echogenicity (reduced echo reflectivity).
- Computed tomography (CT): with contrast enhancement (post-contrast CT), the lesions appear as mildly heterogeneous masses with decreased density (low-attenuation lesion) compared to normal tissue.
- 18F-FDG PET/CT: tumor lesions demonstrate high metabolic activity, actively taking up the radiopharmaceutical (FDG avid).
Comparison of imaging modalities
A key feature of the radiological diagnosis of splenic lymphoma is the varying sensitivity of the methods used.
Practice shows that ultrasound and positron emission tomography (PET/CT) are able to detect a greater number of pathological lesions in the organ. Conventional computed tomography (CT), despite contrast enhancement, may miss some small or isodense lesions, making it less informative in assessing the true extent of the process compared to combined and ultrasound techniques.
Differential diagnosis
When focal or diffuse changes in the spleen are detected, lymphoma must be differentiated from a number of other pathologies described in diagnostic radiology:
- Melanoma metastases: on portal venous phase CT, they also present as low-density foci, and on PET/CT they actively take up FDG.
- Sarcoidosis: causes splenomegaly (homogeneous on unenhanced CT). In the delayed phase, weakly enhancing 2–3 cm nodules are visible.
- Amyloidosis: can occur in nodular or diffuse forms. It is characterized by decreased density on CT and a high probability of organ rupture due to vascular fragility.
- Extramedullary hematopoiesis: can form tumor-mimicking masses. The MRI signal depends on the "age" of the lesion (active vs. old).
Briefly: answers to topical questions
How to distinguish extramedullary hematopoiesis from splenic lymphoma on MRI?
It is impossible to reliably differentiate extramedullary hematopoiesis from lymphomatous involvement of the spleen on MRI, especially in infiltrative lymphoma, because normal and lymphoma-infiltrated tissue may have similar signal intensity.
In focal lesions:
| Sign | Lymphomatous involvement of the spleen | Extramedullary hematopoiesis |
|---|---|---|
| T1-weighted imaging | Slightly hypointense signal | Intermediate signal in active lesions or hypointense signal in old lesions |
| T2-weighted imaging | Hyperintense signal | High signal in active lesions or hypointense signal in old lesions |
| Contrast enhancement | The referenced sources do not specify the contrast enhancement characteristics of MRI lesions | Active lesions enhance with contrast, while old lesions may not enhance |
Class and exam questions
Which method best detects the number of lesions in splenic lymphoma?
Ultrasound and PET/CT show a greater number of tumor nodes in the splenic parenchyma compared to computed tomography.
What do lymphoma lesions look like on contrast-enhanced CT?
They are visualized as mildly heterogeneous masses with decreased density (low-attenuation lesions).
Does splenic lymphoma take up contrast on PET/CT?
Yes, lymphoma lesions actively take up fluorodeoxyglucose (18F-FDG), demonstrating high metabolic activity.
What else to study on this topic
- MRI findings of Gandy-Gamna bodies in portal hypertension
- Diagnosis of splenic amyloidosis and the risks of rupture
- CT and MRI manifestations of hemosiderosis
- Gaucher disease: MRI signs of glucocerebroside accumulation
- Extramedullary hematopoiesis: differentiation of active and old lesions on MRI
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