Seventeen year old teenager (same patient than part 1). Heart transplant one year before exam. Abdominal pain and fatigue. Rule out PTLD.
Large abdominal hypermetabolic mass located near sigmoid (SUV max 10). There is hypermetabolism in the periphery of the lesion; the center is hypometabolic. No FDG-avid lymph node.
There is a urinary stasis in the right kidney, especially in the cortex. The right kidney is mildly larger than the left. There is a pelvic dilation in comparison to the other side. This is likely related to an acute obstruction from the mass.
Part 2: PTLD
PTLD refers to a heterogeneous group of lymphoproliferative disease that develops as a consequence of immunosuppression in transplanted recipient, particularly with solid organs. EBV seems to play an important role in this disorder. EBV infected B-cell are normally in a latency state in immunocompetent, because of the cytotoxic T-cell surveillance. With immunosuppression, this T-cell system is reduced and probability of uncontrolled proliferation of EBV infected B-cell increases.
PTLD in children occurs more frequently in the first two years after transplantation, during the most immunosuppressive period. There are three major risk factors associated with PTLD: EBV status at the time of transplant, age and organ transplant. An EBV-seronegative recipient receiving an EBV-positive allograft is the most significant risk factor. Young age is an independent risk factor. The heart-lung transplant has the highest risk while renal transplant has the least in solid transplant.
The 2008 WHO classifies PTLD in four groups:
-Monomorphic PTLD (subdivided in lymphoma they resemble, most commonly diffuse large B cell and Burkitt lymphoma)
-Classical Hodgkin lymphoma type PTLD
Discrimination between types are made through pathological findings. Early lesions tend to regress with reduction of immune suppression. Polymorphic PTLD may also regress with reduction of immune suppression. A proportion of polymorphic PTLD and numerous monomorphic PTLD needsadditional therapy such as monoclonal antibody (anti CD-20) and chemotherapy.
In PTLD, there is more extra nodal involvement, especially in the abdomen than in lymphoma of immunocompetent patients. Early disease can be found in the tonsils and adenoids, making the diagnosis with PET-FDG difficult, due to physiological uptake in the ENT region.
Roles of TEP-FDG are similar than in conventional lymphomas. It is useful for staging purposes and establishing response to therapy. It can also targets the easiest/best lesion to biopsy. Moreover, one report suggested that most aggressive subtypes (monomorphic PTLD) demonstrate higher metabolic activity.
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