Splenic lymphoma, also termed as lymphomatous involvement of the spleen, represents the most common malignancy to involve the spleen. They are commonly secondary, rarely being primary (referred as primary splenic lymphoma).
This article focuses on the location-specific primary and secondary lymphomas involving the spleen, for a broader and systemic discussion, please refer to the main article on lymphoma.
The spleen is involved in about 30% of all Hodgkin lymphoma and 30-40% of patients with systemic non-Hodgkin lymphoma (NHL) 2,4. The primary splenic lymphoma is rarer, representing about 2% of all lymphomas 2.
Lymphoma can often present with B symptoms (fever, night sweats and weight loss 3), please refer to the main article for further discussion in the systemic presentation.
Both primary and secondary splenic lymphoma may cause left upper quadrant pain 3.
Primary splenic lymphomas are in general due to diffuse large B-cell lymphoma (DLBCL) 4. Please refer to the main article on lymphoma for further discussion in the secondary involvement of the spleen.
Splenomegaly is perhaps the most common manifestation on imaging, but a normal size spleen does not exclude lymphoma involvement 2,3. The most common criteria to determine splenomegaly on imaging is the measurement of the organ craniocaudal height, which is considered normal when less than 13 cm 4.
Associated enlarged splenic hilum lymph nodes may be seen either in the primary or secondary forms. The secondary form will show signs of disease involving other organs and systems, particularly nodal disease.
The focal disease may manifest as small circumscribed nodules, sometimes referred as a milliary pattern, or bulky splenic masses 2 and, generally, these are hypoechogenic on ultrasound. A diffuse infiltrative disease is usually only characterized as an enlarged spleen 3.
- post-contrast images: the focal lesions are hypoenhancing compared to the background parenchyma and they are best appreciated in a late venous phase, particularly when the lesions are small 4
- calcification of the splenic lesions is uncommon but might be seen after treatment 4
Single or multifocal disease will present as well-defined masses 1-2:
- T1: low to iso-intensity compared to the background parenchyma
- T2: low to iso-intensity compared to the background parenchyma
- T1 C+ (Gd): focal lesions will have a mild or absent enhancement compared to the background parenchyma (hypo enhancing lesions) 2,3
- DWI: relatively low ADC values inferring diffusion restriction 3
PET has become the imaging modality of choice to stage and follow-up of Hodgkin and aggressive forms of NHL disease 4.
Splenic lymphoma can manifest on PET either as a diffusely FDG-avid spleen, in cases of a diffuse infiltrative disease, or as single or multiple FDG-avid focal splenic lesions 4.