A para-gastric lesion 13 years after a heart transplant

A 66-year-old male presented with abdominal pain, chronic diarrhoea, and weight loss. He underwent a heart transplant 13 years ago due to heart failure secondary to myocardial infarction. He has been on chronic immunosuppressive therapy and has a 40 pack-years history of smoking cigarettes.

An abdominal CT scan with contrast revealed a 5 cm solid lesion adjacent to the stomach in the left upper quadrant (Figure 1).

A PET/CT scan showed-

1. A hypermetabolic left upper quadrant mass in the abdomen along with multiple hypermetabolic diaphragmatic and mesenteric lymph nodes (Figures 2a, 2b, and 2c).
2. A hypermetabolic pulmonary nodule in the right upper lobe (Figure 3).

The perigastric lesion was biopsied and it showed large, atypical lymphoid cells that were strongly and diffusely positive for CD20, CD10, and BCL-6. In-situ hybridisation for Epstein Barr virus (EBV) was negative. A diagnosis of a high-grade B-cell lymphoma (monomorphic post-transplant lymphoproliferative disorder) was made.

Post-transplant lymphoproliferative disorders (PTLD) are lymphoid and/or plasmacytic proliferation occurring after transplantation (solid organ or hematopoietic cell transplant) in the setting of immunosuppression.

PTLDs are classified as early lesions, polymorphic lesions, monomorphic lesions, plasmacytoma-like lesions and classical Hodgkin’s lymphoma-type PTLD [1,2]. PTLDs are either EBV-positive or EBV negative. Although EBV-driven PTLDs are well understood, the underlying mechanism of EBV-negative PTLDs is not yet clear [1]. EBV-negative PTLDs could occur either due to a transient EBV infection, CMV, another unknown virus, persistent antigen stimulation by the graft and/or prolonged immunosuppression [1].

Monomorphic PTLD is characterised by monoclonal proliferation of lymphoid cells and meets the criteria of at least one of the recognized types of lymphoma. The majority of monomorphic PTLDs are non-Hodgkin’s lymphoma (NHL) of B-cell origin, especially diffuse large B-cell lymphomas (DLBCL) [2,3,4]. Early-onset PTLDs (<1 year after transplant) are often EBV-positive whereas late-onset PTLDs are EBV-negative [5]. Although EBV-positive and EBV-negative PTLDs can be distinguished on a molecular genetic basis, they are clinically indistinct and EBV serostatus does not have any prognostic value [1].

A histopathological examination and immunohistochemistry of the biopsy confirm the diagnosis of monomorphic PTLD. Since monomorphic PTLD is often associated with extranodal involvement, an FDG-PET/CT is recommended [3,6]. The gastrointestinal tract (stomach, intestines) is the most commonly involved extranodal site, followed by the lungs, skin, CNS and the allograft itself [6,7]. FDG-PET/CT is superior to contrast-enhanced CT (lower sensitivity) in the assessment of lymphoma patients hence making it the imaging modality of choice [6].

PTLDs are a serious and potentially fatal complication among transplant recipients. Treatment options include reducing the immunosuppression, rituximab and/or chemotherapy [1]. Re-transplantation after the complete resolution of PTLD is a potential option as well.  Follow-up scans are instrumental in tracking the response to therapy. Our patient received a regimen of R-CHOP and is currently in remission.

Transplant recipients receive immunosuppressive therapy to reduce the risk of graft rejection. However, their immunosuppressed status puts them at a higher risk of developing lymphomas. Patients usually present with vague and generalised symptoms. A suspicion for PTLD is warranted in a setting of transplant and immunosuppression. As findings suggestive of extranodal involvement may be absent on a CT scan, PET is routinely recommended in such patients [6].

Written informed patient consent for publication has been obtained.