PET versus PET-CT in patient with suspicion of non-Hodgkin lymphoma recurrence

We present the case of a 62-year-old patient with a history of non-Hodgkin lymphoma (stage III) in complete remission after 6 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone with rituximab (CHOP-R) in 2006. The patient was referred for a PET-CT scan because of suspicion of recurrence. On PET there were multiple lung lesions, a submandibular lesion (right side) and an impressive retroperitoneal mass with a hypermetabolic wall, and central necrosis invading all retroperitoneal structures (aorta). There was also an additional lesion in the anterior abdominal wall below the liver. It was concluded that it was recurrent non-Hodgkin lymphoma (stage IV). Contrast enhanced CT demonstrated a large, rupturing abdominal aortic aneurysm (AAA) with saccular ectasia of the posterior wall compatible with a mycotic aneurysm. The other sites of hypermetabolism corresponded to metastatic infectious lesions. Histopathology confirmed the mycotic infection. The patient underwent urgent surgery including bilateral axillofemoral stenting and removing a clot from the AAA twice. Intravenous antibiotics were started. This case clearly denotes the importance of contrast enhanced hybrid PET-CT systems in which the CT information is relevant for PET interpretation and not only for anatomic repair. With PET alone, the diagnosis would have been completely different.