The normal spleen typically demonstrates mild diffuse FDG uptake, less than or equal to liver uptake.
Focal increased FDG uptake in the spleen is highly suspicious for malignancy. These malignant lesions may be poorly visualized on the co-registered non-contrast CT images.
Non-avid, low attenuation lesions are nearly always benign (typically representing cysts, hemangiomas or fully treated malignant lesions).
Diffuse increased uptake (greater than liver uptake) can reflect:
- Malignancy (typically active lymphoma); or
- “Splenic Activation” due to recent administration of colony stimulating factors and/or recent chemotherapy (addressed in detail, here). Associated splenomegaly may be present.
- Mild diffuse splenic uptake can also be seen as the sequela of infection or anemia.
Case 1
Case 1 (Image 2)
Normal MIP appearance of the spleen. The metabolic activity of the spleen (white circles) should be less than or equal to liver uptake (black circles).
Case 1 (Image 3)
Normal fused coronal PET/CT appearance of the spleen. In each case, the metabolic activity of the spleen is less than or equal to liver uptake.
Case 2
Case 2 (Image 2)
Axial images reveal a well-defined splenic hypodensity, not significantly FDG-avid. Non-avid splenic lesions typically represent cysts, hemangiomas or treated metastases (hemangioma in this case).
Case 3
Case 3 (Image 2)
MIP and axial images demonstrate splenomegaly and diffuse increased metabolic activity of the spleen (uptake greater than liver uptake). As there is no history of recent chemotherapy and/or colony stimulating factors, the appearance is highly suspicious for active malignancy (active lymphomatous involvement of the spleen in this case).
Case 4
Case 4 (Image 2)
Axial images pre- and post-therapy demonstrate splenic activation secondary to recent chemotherapy.
Case 4 (Image 3)
Coronal images pre- and post-therapy demonstrate splenic activation secondary to recent chemotherapy. Such activation can result in splenomegaly.