PMC7357051_01
FDG-PET showing increased uptake at site of rectal tumor (top arrow) and presacral lymph node (bottom arrow). While FDG-PET did not pick up any activity in the prostate, it cannot be ruled out that a possible reason for lack of uptake was due to washout from a more intense signal from the rectal lesion as shown in the top arrow.
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Given the incidental finding of prostatic enlargement and possible sclerotic bone lesion of the left iliac crest appearing quite suspicious, an FDG-PET scan was done and confirmed the primary rectal tumor with a presacral lymph node, but did not reveal any increased uptake in the prostate or iliac crest (Figure 1).
PSMA-PET showing increased uptake in the prostate (red arrow).
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PSMA-PET revealed increased uptake in the prostate, which was not previously detected by FDG-PET (Figure 2).
PSMA-PET showing a lesion in the iliac crest (red arrow), but without uptake (yellow).
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There was no uptake in the iliac crest (Figure 3).
Sagittal MRI showing a left iliac bone lesion, which was classified as an intraosseous lipoma by the radiologist due to defined margin and central necrosis.
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After careful evaluation by the radiologist and nuclear medicine physician, it was determined that given the appearance of the lesion on MRI as calcification with well-defined margins and central necroses and the lack of uptake by PSMA-PET, which is highly sensitive for prostate metastases, the lesion likely represented an intraosseous iliac lipoma instead of a metastasis (Figure 4).