Splenic lymphoma is the most common malignant tumor of the spleen and can occur in primary or secondary (systemic) form. Primary splenic lymphoma is rare and confined to the spleen; the secondary form is much more common and usually part of systemic non-Hodgkin lymphoma (NHL) or Hodgkin lymphoma (HL) involvement. Among NHL types, diffuse large B-cell lymphoma (DLBCL), marginal zone lymphoma (splenic type — SMZL), and mantle cell lymphoma most commonly involve the spleen. Splenic involvement presents in four patterns: (1) diffuse homogeneous infiltration (splenomegaly — most common), (2) miliary pattern (numerous small nodules, <1 cm), (3) multiple focal lesions (1-10 cm), (4) large solitary mass (rare). Splenomegaly is the most common presentation and may sometimes be the only finding. B symptoms (fever, night sweats, weight loss) frequently accompany. Splenic involvement is classified as stage III in the Ann Arbor staging system.
Age Range
20-80
Peak Age
55
Gender
Male predominant
Prevalence
Common
Splenic lymphoma represents clonal proliferation of lymphoid cells within the splenic parenchyma. As the largest organ of the lymphoid system, the spleen is a natural lymphoma target through its periarteriolar lymphoid sheaths (PALS — T-cell zone) and marginal zone (B-cell zone) in white pulp. Lymphoma cells infiltrate and expand these anatomical compartments. In the diffuse infiltration pattern, lymphoma cells spread homogeneously throughout red and white pulp — sinusoidal dilatation and organ enlargement occur, presenting as homogeneous splenomegaly without focal lesions on imaging. This pattern is particularly seen in small lymphocytic/lymphoplasmacytic lymphoma and hairy cell leukemia. In the focal nodular pattern, lymphoma cells form focal masses; these masses are homogeneous solid, hypovascular, appearing as hypodense/hypoechoic lesions on imaging. Hypovascularity means less vascularization than normal splenic parenchyma, explaining the hypodensity on CT and hypoechogenicity on US. They show diffusion restriction on DWI because dense cellular packing (increased cellularity, high nucleus-to-cytoplasm ratio) restricts free Brownian movement of water molecules.
The combination of multiple homogeneous hypodense/hypoechoic lesions with splenomegaly and marked diffusion restriction on DWI (low ADC <1.0 × 10⁻³ mm²/s) is highly suggestive of splenic lymphoma. The homogeneous nature of lesions, minimal enhancement, and absence of necrosis support this diagnosis.
Homogeneously hypodense lesions are seen relative to splenic parenchyma in the portal venous phase. Lesions are typically round or oval, with smooth margins. Enhancement is minimal or mild — the significant enhancement expected in solid tumors is absent. Necrosis is generally not prominent (except aggressive DLBCL). Lesions may be multiple (most common pattern) or rarely present as a solitary mass. The density difference between splenic parenchyma and lesion is typically 20-30 HU. Splenomegaly frequently accompanies.
Report Sentence
Multiple homogeneously hypodense lesions are seen in the spleen on portal venous phase with minimal enhancement; splenomegaly accompanies and lymphomatous involvement should be primarily considered.
In the arterial phase, focal hypodense lesions may be harder to identify against the background of the spleen's normal zebra pattern heterogeneous enhancement. Splenomegaly is prominent (long axis >13 cm). In diffuse infiltration pattern, focal lesions may not be visible — only an enlarged homogeneous spleen is seen. In miliary pattern, numerous small (<1 cm) hypodense nodules are scattered throughout the splenic parenchyma. A disproportionately low lesion count relative to increased splenic size ('big spleen, small lesions') should raise suspicion for lymphoma.
Report Sentence
Prominent splenomegaly is noted with multiple millimetric hypodense foci in the splenic parenchyma in the arterial phase, which may be consistent with miliary involvement.
On DWI (b=800-1000 s/mm²), lymphoma lesions show marked diffusion restriction — hyperintense signal at high b-value. Low ADC values (typically <1.0 × 10⁻³ mm²/s) are detected on ADC maps. Diffusion restriction reflects the high cellularity of lymphoma and is very valuable in differentiation from other splenic lesions (hemangioma, cyst, abscess). Even in diffuse infiltration pattern, ADC values are lower than normal splenic parenchyma — this is an important clue suggesting lymphomatous involvement even when focal lesions are not seen.
Report Sentence
The splenic lesions demonstrate marked diffusion restriction on DWI with low ADC values; this finding is consistent with high cellularity and supports lymphomatous involvement.
On T2-weighted MRI, lymphoma lesions show mildly to moderately hyperintense signal relative to splenic parenchyma. Signal increase is much less pronounced than the marked 'light bulb sign' hyperintensity of hemangioma — this is critical for differential diagnosis. Homogeneous signal pattern is typical (necrosis or hemorrhage is generally absent). In diffuse infiltration pattern, splenic signal homogeneity may be preserved but organ size is increased.
Report Sentence
The splenic lesions show mildly to moderately hyperintense, homogeneous signal relative to the splenic parenchyma on T2-weighted MRI.
On B-mode ultrasonography, homogeneously hypoechoic lesions are seen relative to the splenic parenchyma. Lesions are well-defined, round or oval with generally homogeneous internal echoes. Splenomegaly accompanies (long axis >13 cm). In miliary pattern, numerous small hypoechoic nodules are seen. 'Target sign' (hypoechoic center surrounded by peripheral hyperechoic rim) may be observed in some cases. In diffuse infiltration pattern, splenic size is increased but echotexture may be normal.
Report Sentence
Multiple well-defined, homogeneously hypoechoic lesions are seen in the spleen on US with accompanying splenomegaly; lymphomatous involvement should be considered in the differential diagnosis.
On FDG PET-CT, lymphoma lesions demonstrate markedly increased FDG uptake. SUVmax values are typically >5, reaching >15-20 in aggressive types (DLBCL). Focal lesions appear as 'hot spots' while diffuse infiltration pattern shows homogeneously increased uptake throughout the spleen. PET-CT is superior in detecting miliary or diffuse involvement hidden on CT. In treatment response evaluation (Deauville/Lugano criteria), SUVmax change is prognostically significant.
Report Sentence
Markedly increased metabolic activity is seen in the spleen on FDG PET-CT with elevated SUVmax values; consistent with lymphomatous involvement.
On T1-weighted MRI, lymphoma lesions show hypointense or isointense signal relative to splenic parenchyma. Homogeneous signal pattern is typical — necrosis or hemorrhage is generally absent (except aggressive DLBCL). Mild to moderate homogeneous enhancement is seen on contrast-enhanced T1 series — the hypovascular structure of lymphoma limits gadolinium distribution but minimal vascularity is present. Splenomegaly accompanies.
Report Sentence
The splenic lesions show hypointense signal relative to splenic parenchyma on T1-weighted MRI with mild homogeneous enhancement on post-contrast series.
Criteria
Most common aggressive NHL type. Single or multiple large masses (>5 cm). Rapid growth, very high SUVmax.
Distinct Features
Heterogeneous enhancement and internal necrosis may be seen (unlike other lymphoma types). Aggressive clinical course. Good response to R-CHOP chemotherapy.
Criteria
Indolent NHL. Prominent splenomegaly, miliary pattern (small nodules). Lymphocytosis and villous lymphocytes on peripheral smear.
Distinct Features
Miliary pattern is most prominent in this type. Hepatitis C association (30%). Splenectomy alone may be curative. Slow progression.
Criteria
Usually in context of systemic disease. Young adults. Mediastinal LAP frequently accompanies.
Distinct Features
Focal lesions usually well-defined and homogeneous. PET-CT is gold standard in staging and response assessment (Deauville criteria). Excellent prognosis.
Criteria
Massive splenomegaly, pancytopenia, dry tap bone marrow aspiration. Focal lesions rarely seen.
Distinct Features
Diffuse infiltration pattern — prominent homogeneous splenomegaly without focal lesions. BRAF V600E mutation. Excellent response to cladribine therapy.
Distinguishing Feature
Metastasis usually shows irregular margins, heterogeneous enhancement, and necrosis/cystic degeneration; lymphoma is homogeneous, well-marginated with minimal enhancement. Metastasis is considered with known primary tumor.
Distinguishing Feature
Sarcoidosis usually shows small (<2 cm) hypodense nodules but accompanied by bilateral hilar LAP, pulmonary involvement, and elevated ACE; in lymphoma, B symptoms and different LAP pattern are expected.
Distinguishing Feature
Abscess shows rim enhancement and internal fluid/gas level; lymphoma shows homogeneous minimal enhancement. Abscess patients present with fever, leukocytosis, and immunosuppression/endocarditis history.
Distinguishing Feature
Angiosarcoma shows heterogeneous enhancement, hemorrhage (T1 hyperintense foci), and aggressive behavior; lymphoma is homogeneous and hemorrhage-free. Angiosarcoma is very rare and presents with widespread metastases.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
specialist-referralTissue sampling is required for splenic lymphoma diagnosis — histopathological verification via splenectomy or percutaneous biopsy (considering bleeding risk). PET-CT is critical for staging and treatment response evaluation (Deauville/Lugano criteria). Treatment determined by lymphoma type: aggressive NHL (DLBCL) → R-CHOP, indolent NHL (SMZL) → observation or rituximab, Hodgkin → ABVD. Hematology consultation mandatory.
Splenic lymphoma is often part of systemic disease and biopsy is usually unnecessary when systemic lymphoma is diagnosed. In isolated splenic lymphoma, splenectomy is both diagnostic and therapeutic.