A 69-year-old man was referred to our hospital with abdominal pain. He underwent a kidney transplantation three and a half years ago due to chronic renal failure caused by progressive nephrosis and was taking immunosuppressants, tacrolimus, and mycophenolate mofetil. Physical examination revealed mild tenderness around the umbilicus. The computed tomography (CT) scan showed rapidly enlarging soft tissues around the duodenum as well as multiple nodules in the peritoneum and mesentery. 18F-Fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) revealed marked accumulation in the multiple nodules extensively distributed throughout the entire abdominal cavity (Figure 1A,B). Endoscopic ultrasound-guided fine-needle aspiration of the soft tissues around the duodenum revealed proliferation of medium-sized B cells positive for CD20, CD10, BCL6, c-MYC, and Ki-67 (the proliferation index, nearly 100%), but negative for CD3, cyclin D1, BCL2, and EBV encoded small RNA (EBER) in situ hybridization (Figure 1C–G). Thus, the diagnosis of peritoneal lymphomatosis as an aggressive type, monomorphic posttransplant lymphoproliferative disorder (PTLD) was made. Cytogenetic analyses, including fluorescence in situ hybridization (FISH), could not be performed due to the limited biopsy specimen; however, the immunohistochemical findings were consistent with Burkitt lymphoma, EBV, and posttransplant setting, according to the 5th edition of the WHO Classification of Haematolymphoid Tumours: Lymphoid Neoplasms 1. He was initially treated with two cycles of dose-reduced Pola-R-CHP (polatuzumab vedotin with rituximab, cyclophosphamide, doxorubicin, and prednisolone) therapy due to concerns about the risk of tumor lysis syndrome. After confirming the safety and efficacy, the treatment was switched to dose-adjusted (DA)-EPOCH-R (etoposide, prednisolone, vincristine, cyclophosphamide, doxorubicin, and rituximab) therapy, which was administered for four cycles. Regarding immunosuppressants, the dose of tacrolimus was reduced, mycophenolate mofetil was discontinued, and everolimus was introduced with the expectation of its potential antitumor effect. After a total of six cycles of chemotherapy, a complete response was obtained, and renal function was also maintained. PTLD is a serious complication that develops after organ transplantation or allogeneic hematopoietic stem cell transplantation, and immunosuppressive agents and EBV have been presumed to be implicated in the pathogenesis of this disease 2. Peritoneal lymphomatosis is a rare subtype of non-Hodgkin lymphoma characterized by diffuse lesions in the peritoneum, omentum, and mesentery. Early diagnosis of this condition by using PET/CT is particularly important for patient management 3. To the best of our knowledge, only a few cases with peritoneal lymphomatosis as PTLD have been reported 4, 5. One case was after liver transplantation, and the other was after kidney transplantation. In these reports, the period from transplantation to peritoneal lymphomatosis onset was 8–15 years, with no involvement of EBV, and considered as a late-onset lymphoma. Treatment of adjusting immunosuppressants and administering chemotherapy, including rituximab, induced a complete response in all cases, but one case experienced recurrence. We considered this case as highly aggressive Burkitt lymphoma and treated with an intensified regimen of DA-EPOCH-R 6, which resulted in a complete response. Therefore, although a rare manifestation of lymphoma, we should be aware of late-onset peritoneal lymphomatosis as PTLD and the usefulness of PET/CT in patients following organ transplantation. All authors were involved in the management of the patient. They have contributed to the writing of the manuscript and agreed to the submission of the manuscript. We thank Dr. Eiji Kudo (Department of Diagnostic Pathology, Tokushima Prefecture Central Hospital, Tokushima, Japan) for the pathological diagnosis. The authors have nothing to report. The publication of this case was approved by the Ethical Committee of Tokushima Prefecture Central Hospital. Written informed consent was obtained from the patient for publication of this case and accompanying images. The authors declare no conflicts of interest. The original data of this study can be obtained from the corresponding author.
Nishitani et al. (Wed,) studied this question.