Posttransplant lymphoproliferative disorder (PTLD), a potentially malignant process, is an occasional complication of immunosuppression after solid-organ transplantation. It generally manifests during the 1st posttransplant year (1–3) and represents abnormal proliferation of B-cells in response to either primary or reactivated infection with the Epstein-Barr virus (EBV) (4–6). An increased risk for PTLD has been associated with EBV seronegativity at the time of transplantation (1, 7) and with immunosuppressive regimens that include OKT3® monoclonal antibody (1, 8–10). It occurs in 0.9 to 2.5% of renal transplant recipients (1, 3, 10–14), and at a higher rate in recipients of heart, lung, and heart-lung allografts (3, 12, 15), presumably reflecting more intensive immunosuppressive therapy. In renal transplant recipients PTLD usually presents as a systemic disease involving lymphoid tissue, spleen, or the central nervous system (2, 12). Occasional allograft-localized disease has been reported (1, 16–23). In recent years, we noted what seemed to be an unusual frequency of this latter variant. We report 10 renal transplant recipients presenting with acute renal dysfunction caused by PTLD, involving only the allograft.
MATERIALS AND METHODS
Between January 1, 1993 and December 31, 1997, 1474 patients underwent renal transplantation at the University of Alabama at Birmingham (UAB). In a retrospective analysis, 14 patients with PTLD were identified and their medical records were reviewed. We compiled data on their clinical presentation, race, sex, donor characteristics, immunosuppressive therapy, frequency and severity of rejection, cause of end stage renal disease (ESRD), imaging studies, histological features of tumors, and clinical outcome. The Cockroft –Gault formula was used to estimate creatinine clearance (24).
During the study period, all recipients of cadaver-donor, and zero- and one-haplotype living-donor allografts received OKT3® as induction immunosuppressive therapy. Azathioprine (Imuran®) or mycophenolate mofetil (CellCept®) was given perioperatively and restarted on postoperative day 2. Cyclosporine (Neoral® or Sandimmune®) was started when the serum creatinine decreased below 3.0 mg/dl. Methylprednisolone 500 mg was administered intraoperatively and the dose was tapered during the first postoperative week. Prednisone 30 mg per day was substituted for methylprednisolone before discharge. All patients received prophylactic antiviral therapy for a minimum of 3 months after transplantation, either acyclovir or ganciclovir.
All imaging studies were retrospectively reviewed by two radiologists (RL-B, JKS). Ultrasound examinations were performed with an Acuson 128XP-10 or Acuson Sequoia 512 and a 4 mHz sector transducer. Grey scale settings were individually optimized, and Doppler imaging (color, spectral, power) settings were optimized for detection of low flow. Data were compiled for mass size, echogenicity, location, and relationship to renal hilar vessels with special attention to dilatation of the renal collecting system, or stenosis of the renal vein or artery. Renal vascular stenosis was calculated on spectral Doppler assessment as a focal increase in blood flow velocity greater than twice that in the adjacent iliac inflow vessels. Computerized tomography (CT) examinations were performed with General Electric 9800 Hi-speed or Hi-light, using standard collimation and table speed. A General Electric Signa 1.5 T magnet was used for the magnetic resonance (MR) imaging. The CT and MR imaging studies were reviewed for attenuation or signal characteristics of the mass, presence, and pattern of contrast enhancement, and enlargement of any pelvic or abdominal lymph node. PTLD was considered present when a solid renal hilar mass was identified, usually intimately involving the renal vessels, with some minimal enhancement on CT or MR imaging (25).
Histological tissue samples were processed and stained with hematoxylin and eosin, periodic acid-Schiff, and trichrome by routine clinical methods. Specimens were stained for EBV using antibody for latent membrane protein-1. For gene detection studies, a small sample of the tumor was processed and DNA was amplified in polymerase chain reaction, size-fractionated through agarose, and transferred to a nylon support membrane. The sample was then analyzed with a radiolabeled probe specific for the EBV Bam HI W fragment. For flow cytometric analysis, a small sample of the tumor was minced, and cells were recovered by Ficoll separation. These cells were tested for B-cell- , T-cell- , and non-lineage-specific antigens, using a panel of clinically-defined monoclonal antibodies.
In patients in whom EBV was detected in tumor cells, samples of stored, frozen sera obtained preoperatively on the day of transplantation were analyzed for EBV viral capsid antigen immunoglobulin G by ELISA (Gull Laboratories, Inc. Salt Lake City, Utah).
Clinical presentation and demographics.
There were 14 patients with PTLD identified. Four patients had systemic disease: peripheral lymphadenopathy (2), central nervous system disease (1), or pulmonary infiltrate with pleural effusion (1). Only one of the four patients was febrile at presentation. All received OKT3® with induction immunosuppressive therapy (mean dose 32.5±12.6 mg, range 15–45 mg). Two patients who developed acute rejection and were treated with methylprednisolone; one of these two also received equine antithymocyte globulin for 8 days. There were 10 other patients with disease apparently localized near the renal allograft, and they made up 0.7% of all recipients. The mean posttransplant interval to diagnosis was 221±70 days (range 114–360 days). All patients presented with renal dysfunction. The mean serum creatinine was 3.0±1.0 mg/dl, corresponding to an estimated creatinine clearance of 41±15 ml/min, and was 1.1±0.9 mg/dl (range 0.4–2.8 mg/dl) above the baseline value. This change represented a 35±15% decline in estimated creatinine clearance. Four patients were febrile at presentation. No patient had clinically apparent lymphadenopathy at presentation or at any time later.
Patients with localized PTLD were more likely to be recipients of cadaveric allografts and to be undergoing hemodialysis at the time of engraftment. The leading cause of ESRD in the localized PTLD group was hypertension (n=3); other causes included polycystic kidney disease (n=1), diabetic nephropathy (n=1), lupus nephritis (n=1), focal segmental glomerulosclerosis (n=2), and undefined disorders (n=2). Among the 10 cadaveric donors for the localized PTLD group, the mean age was 22±12 years, 50% were African American, 40% were female, and the mean HLA A, B, DR match with the recipients was 2.5±2.0 antigens. There were 9 of 10 recipients undergoing induction therapy with OKT3® monoclonal antibody, with a mean dose of 45±12 mg (range 35–65 mg). Four patients developed acute rejection in the early postoperative period and were treated with methylprednisolone, with the cumulative doses ranging from 2000 to 4000 mg; one of these patients also received OKT3® for 11 days.
The key findings from the imaging studies are summarized in Table 1. All 10 patients had undergone Doppler ultrasound examination, which documented a mass in the renal hilum adjacent to the vessels that exhibited mixed echogenicity with hypoechoic and hyperechoic elements (Fig. 1). Five patients demonstrated distention of the urinary collecting system (mild in 2 patients, moderate to marked in 3 patients). Eight patients had focal stenosis of renal vessels caused by mass effect: the main renal artery in four, the main renal vein in three, and both in one. Seven patients also underwent CT examinations of the abdomen and pelvis (four studies without i.v. radiocontrast). The hilar masses had predominantly low attenuation and showed mild diffuse enhancement when contrast was administered (Fig. 2). Six patients were evaluated with MR examinations. The signal characteristics were heterogeneous with isointensity to hypointensity on T1 (with respect to signal intensity for muscle), slightly increased T2 signal (although less than that of the parenchyma of the renal allograft), and minimal contrast enhancement (Fig. 3). No patient had intra-abdominal or pelvic lymphadenopathy by CT or MR studies. One patient with urinary obstruction underwent a percutaneous nephrostogram that showed extrinsic compression of the ureter caused by a hilar mass.
After PTLD was diagnosed, immunosuppressive therapy was markedly reduced. Three of the four patients with systemic disease underwent multi-drug chemotherapy. Despite treatment, all four patients died 585±422 days (range 46–1000 days) after the diagnosis. Among the 10 patients with PTLD localized near the allograft, the mean reduction in cyclosporine dose was 53±37% and the mean reduction of azathioprine or mycophenolate mofetil dose was 43±42%. Four patients were given antiviral therapy with either acyclovir or ganciclovir. Three patients are living with functional allografts, without clinical or imaging evidence of progressive disease: two more than 2 years after the diagnosis and one with a recent diagnosis (July 1998). Each patient undergoes periodic ultrasonography or CT scanning to monitor the size and characteristics of the hilar mass. In seven patients, an allograft nephrectomy was indicated for acute rejection caused by decreased immunosuppression (n=4), progressive renal dysfunction (n=1), or enlargement of the mass (n=2). No patient subsequently developed lymphadenopathy or extrarenal disease during follow-up observation of 978±600 days. One patient died, after resuming hemodialysis, from complications of gastrointestinal bleeding, and another died 4 years after a nephrectomy. Neither had evidence of PTLD at the time of death.
Among the seven patients who underwent an allograft nephrectomy, in three the tumor was so intimately associated with hilar structures that safe dissection or biopsy could not be performed without severe complications. In the other four patients, most of the tumor was excised. The pathological findings are summarized in Table 2. One patient had a distinct tumor mass within the renal parenchyma as well as perinephric tumor; in the other three the mass was largely perinephric, although there was infiltration from the perinephric mass into the renal parenchyma in all four. Sections of the tumor from all four cases showed a monomorphic infiltrate of large transformed atypical lymphoid cells (Fig. 4). There was extensive necrosis within the infiltrate and adjacent kidney. In the classification scheme of Harris et al. (26), the four tumors were PTLD-monomorphic. In three patients, the neoplastic cells were characterized by the flow cytometric features of a B-cell monoclonal population with kappa light chains. In the fourth patient, the sample contained an insufficient quantity of viable cells for analysis. Immunostaining for EBV was positive in all resected tumors, and polymerase chain reaction analysis of two specimens revealed EBV genetic material. All nephrectomy specimens demonstrated acute interstitial and vascular rejection. The four patients with EBV-positive tumors tested positive for circulating EBV viral capsid antigen immunoglobulin G antibodies at the time of engraftment.
The prevalence of PTLD in renal allograft recipients receiving transplants at UAB from January 1, 1993 through December 31, 1997, was 1.0%, similar to that reported in other series (1, 3, 10–12, 14). Unlike in the published literature, 72% of our patients had disease localized near the allograft. The mortality in the patients with disseminated disease was 100%; of the 10 patients with localized disease, one died shortly after returning to dialysis and another died 4 years after a nephrectomy. Neither had evidence of PTLD at demise.
Only 12 patients with PTLD localized near the renal allograft have been previously reported (1, 16–23) (Table 3). These cases parallel ours with respect to donor type, time to diagnosis, antibody therapy for induction of immunosuppression, maintenance three-drug immunosuppressive regimen, frequency of rejection before diagnosis, presentation with renal dysfunction, and requirement for a nephrectomy. Likewise, a small fraction of the patients had functional allografts after reduction of immunosuppressive therapy. In contrast to these reported long-term survivors, the three patients at UAB with functional allografts continue to show localized disease, fortunately without dissemination.
The association between PTLD and OKT3® therapy has been observed by Swinnen et al. (9) in heart transplant recipients. Such therapy increased the risk for PTLD 9-fold, compared with the risk in patients not treated with OKT3®. Furthermore, the cumulative dosage was influential; the frequency of disease was 36% in patients receiving >75 mg, in contrast to only 6% for those treated with less. In a study of renal transplant recipients, Melosky et al. found that all patients with lymphoproliferative disorders had received OKT3® (10).
Some investigators have recently speculated that use of mycophenolate mofetil, approved in 1995 for immunosuppression after transplantation, might reduce the risk for lymphoproliferative disorders by inhibiting division of cells infected with EBV (27). However, five of the patients described here developed disease while maintained with mycophenolate mofetil. Whether the overall prevalence of PTLD will be affected by such therapy remains to be determined.
The most helpful diagnostic imaging technique for our patients was ultrasound. The differential diagnosis of a sonographically complex mass adjacent to a renal allograft includes nonneoplastic causes, such as resolving hematoma, seroma, and complicated lymphocele. If blood flow within the mass is shown by a Doppler examination or contrast enhancement by CT or MR imaging, these possibilities are unlikely. PTLD was suggested by imaging when a hilar mass showed vascular stenosis. MR and CT imaging confirmed the hilar location of the solid mass and showed minimal enhancement. This MR imaging pattern has been recently described as typical for PTLD (25). Minimal contrast enhancement on CT or MR studies denoting minimal vascularity is unusual for other neoplasms, such as renal cell carcinoma. The absence of visualized adenopathy or any mass within the renal parenchyma was common in our patients, and helped to distinguish localized disease from systemic lymphoma. Although renal vascular stenosis in a cadaveric allograft with a Carrell aortic patch is occasionally caused by anastomotic narrowing, our experience stresses the need to exclude a constricting hilar mass, especially if dilatation of the urinary collecting system is also observed.
It is interesting that in three patients the main tumor mass was perihilar with only focal extension into the renal parenchyma. The pathological differential diagnosis of a PTLD is generally a lymphoproliferative disorder versus severe rejection. Features that distinguish PTLD include a monomorphic infiltrate of lymphoblasts without edema, patchy necrosis of the lymphoid cells, and nodular aggregates of immature lymphoid cells. Immunohistochemical analysis may also be informative. In rejection, B-cells rarely predominate, whereas almost all PTLDs are B-cell proliferations that are CD20-positive. Stains for EBV nuclear antigens (e.g., EBNA-2) and membrane proteins (e.g., latent membrane protein-1) are usually positive. Detection of EBV genetic material by in situ hybridization will be positive in most, if not all, cases associated with EBV. The four patients in our study with EBV detected in the tumor mass had circulating antibodies against EBV before transplantation. This finding weakens the hypothesis that EBV seronegativity is an important risk factor for the development of PTLD after renal transplantation (7, 9).
To our knowledge, this report constitutes the largest series of renal transplant patients with PTLD localized near the allograft. These 10 patients made up 77% of those affected with PTLD after transplantation at UAB from 1993–1997. All patients presented with renal dysfunction, and ultrasound was the most helpful imaging technique. No patient developed disseminated disease; seven subsequently required a nephrectomy. This variant of PTLD should be considered in the differential diagnosis of allograft dysfunction within the first posttransplant year.
The authors thank Dr. John J. Curtis for editorial comments; Dr. Alan Wells, Ms. Rita Macon, and Ms. Marcia Ward for their assistance in gathering and organizing the data; and Epidemiology Resources Inc. for educational grant support.
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