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ANATOMIC PATHOLOGY
Review Article
Posttransplantation Lymphoproliferative
Disorders
FIONA E. CRAIG, M.D., MARGARET L. GULLEY, M.D., AND PETER M. BANKS, M.D.
ficiency,18"23 PTLDs are unique in regard to potential
resolution with diminished immunosuppression. '-8 Eradication of such invasive, often pleomorphic proliferations by restitution of immune competency also raises
profound questions about the definition of lymphoid
neoplasia. In this review article the difficulties that may
be encountered in making the diagnosis of PTLD are
presented, as is a pathogenetic model to explain the
unique characteristics of this disorder and a summary of
available therapeutic options.
Posttransplantation lymphoproliferative disorders
(PTLDs) currently affect approximately 2% of all organ
allograft recipients.1 This problem has increased in magnitude in recent years both because of newly available
powerful immunosuppressive agents and the steady increase in the number of organs transplanted.2 In 1990
more than 20,000 allogeneic organ transplants were performed in the United States.23 Although individual pathologists are unlikely to acquire a broad experience with
PTLDs, they are likely to encounter occasional cases in
the course of their routine practice. Furthermore, because PTLDs may occur months or even years after
transplantation,4"7 the challenge of diagnosis is not confined to pathologists in health care facilities directly engaged in organ transplantation. It is essential that posttransplantation proliferative disorders be recognized
early, because they can often be cured with appropriate
therapy.1,8 Without accurate diagnosis and appropriate
treatment, these disorders are potentially rapidly
fatal.9"12 The pathologist with little experience with
PTLDs will often render an erroneous diagnosis of lymphoma, applying the criteria for the diagnosis of conventional lymphomas occurring in nonimmunocompromised patients. Lymphoproliferative disorders occurring
in association with immunosuppression, however, are
unique. They have a predilection for extranodal sites,4,13
a varied morphologic appearance,5 a strong and probably causal association with Epstein-Barr virus (EBV) infection,4,614 frequent absence of immunophenotypic6,15
or genotypic6,'6''7 evidence of monoclonality, and a poor
response to the cytolytic chemotherapeutic or irradiation regimens used for lymphoma.6,9"12,18 Although these
features are shared to some extent by tumors occurring
in patients with either congenital or acquired immunode-
DIAGNOSIS
The incidence of PTLD varies with the organ transplanted and with the nature and severity of the accompanying immunosuppressive regimen.7,20,24 Posttransplantation lymphoproliferative disorders affect
approximately 0.6% of patients after bone marrow transplantation,25 1-5% of renal graft recipients,26 and 1.820% of patients after cardiac transplantation.15,16,19"21
The correct and early diagnosis of PTLD is complicated
by its wide spectrum of clinical presentations and the
difficulty in distinguishing it from other more frequent
complications of organ transplantation—allograft rejection and opportunistic infection. The following clinical
symptoms and signs aid in the diagnosis of PTLD and
carry prognostic implications as well.
Clinical Presentation
Posttransplantation lymphoproliferative disorder presents at a variable interval after transplantation. The
length of this interval apparently is related to the immunosuppressive regimen used.1 Currently most allograft
recipients are treated with regimens containing the immunosuppressive drug cyclosporin A (CsA). PosttransDepartment of Pathology, University of Texas Health Science Center plantation lymphoproliferative disorders developing in
CsA-treated patients can occur within 1 month of transat San Antonio, San Antonio, Texas.
plantation,7 and therefore the initial presentation is easAddress reprint requests to Dr. Banks: Department of Pathology,
ily confused with rejection or infection. Similarly, immuUniversity of Texas Health Science Center at San Antonio, 7703 Floyd
nosuppression with anti-T-lymphocyte monoclonal
Curl Drive, San Antonio, TX 78284-7750.
265
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ANATOMIC PATHOLOGY
Review Article
antibodies, e.g., OKT3, also is associated with a high
incidence and early onset of PTLDs.27 In patients receiving regimens with neither CsA nor anti-T-lymphocyte
monoclonal antibodies, PTLD develops no earlier than
several years after transplantation.7
Posttransplantation lymphoproliferative disorder has
a mode of presentation that varies with the organ transplanted, the immunosuppressive regimen, and the age of
the patient.117'20 Although some patients may be asymptomatic or display localized lymphadenopathy, in others
the disease may be widely disseminated and involve multiple organs and lymph node groups.1 The group in
which spread has occurred has a poor prognosis, particularly when there is coexistent sepsis.1 Most frequently
PTLD is localized regionally to a group of nodal or extranodal tissues.117'20 Patients recognized early in the
course of their disease with limited organ involvement
may respond to conservative treatment.1 Included in this
group of responders are those with an infectious mononucleosis-like syndrome characterized by fever, pharyngitis, and cervical lymphadenopathy.4'619 Typically such
patients are young (mean age, 23 years),4 present within
the first 9 months of immunosuppression, and are receiving CsA. This mode of presentation contrasts with
that in older patients (mean age, 48 years), in whom
PTLD arises later after transplantation.20 Although older
patients typically have symptoms of a localized tumor
mass in the setting of less immunosuppression, they respond poorly to therapy.20
Posttransplantation lymphoproliferative disease in patients treated with CsA-containing regimens has a distinct predilection for the gastrointestinal tract.713,28 Patients with disease confined to this system often do well
despite multifocal distribution of their disease and the
frequent complication of visceral perforation.8 Other
sites of localized organ involvement have included the
lung, kidney, prostate, and engrafted organ.14 Although
primary central nervous system disease is relatively common in patients receiving treatment protocols lacking
CsA, inclusion of CsA in the treatment protocol usually
restricts involvement of the central nervous system to
patients with advanced multiorgan dissemination of
PTLD.7-19
Pathologic Diagnosis
The diagnosis of PTLD typically involves both the
clinical and anatomic pathology laboratories. Microbial
detection methods are important in excluding opportunistic infections and may be used to document the presence of EBV.18 Epstein-Barr virus has been identified in
virtually all cases of PTLD using genetic techniques; culture and serologic studies, however, are less sensitive in
detecting EBV. Although serologic studies are some-
times successfully applied to demonstrate primary infection1,29 or reactivation of EBV infection,24 they are not
entirely reliable because a serologic response may be absent or abnormal in immunosuppressed patients.4'6'18
Histologic analysis of tissue biopsies is required to establish the diagnosis of PTLD. Although the results of immunohistochemical and gene rearrangement studies
may have some prognostic bearing, they are of little
value in primarily establishing the diagnosis. Accurate
interpretation of paraffin-embedded tissue sections provides the clinicians with critical information needed for
immediate treatment of the patient.
The histologic diagnosis of PTLD is made difficult by
its wide spectrum of morphologic appearances. This
spectrum has prompted the subdivision of PTLD into
various categories (Table 1). Although we recommend
the simplified morphologic and empiric classifications of
PTLD, the most frequently used classification is that
proposed by Frizzera and co-workers in 1981.5 The authors of this landmark study recognized that PTLDs exhibit a range of histologic appearances, and proposed
that these morphologic features are predictive both with
regard to the presence of clonality and to biologic behavior. They presented a model in which the disorders progressed consistently from polymorphic, polyclonal,
benign lymphoid proliferations to monomorphic, monoclonal malignant disorders.30 The two ends of this histologic spectrum are defined by diseases that have
histologic counterparts in nonimmunocompromised patients—nonspecific reactive hyperplasia manifests histologic features resembling those seen in infectious mononucleosis, whereas immunoblastic sarcoma was defined
as a morphologically uniform proliferation of atypical
immunoblasts. Frizzera proposed also that there are two
intervening distinct phases of PTLD: polymorphic diffuse B-cell hyperplasia and polymorphic B-cell lymphoma. These lymphoid proliferations share a polymorphic cellular composition and the capacity for tissue
invasion; however, polymorphic B-cell lymphoma was
defined as neoplastic because of the presence of extensive necrosis and large, atypical, sometimes multinucleated immunoblasts. Although this classification illustrates the range of histologic appearances encountered in
PTLDs and emphasizes the invasive potential of these
disorders, subsequent investigation has raised doubts
about its scientific validity and prognostic utility.1
PTLDs do not appear to follow such a predictable progression, and the criteria proposed to define malignancy
(cellular atypia and necrosis) neither correlate with demonstration of monoclonality nor predict which patients
will have progressive disease despite reduced immunosuppression.29 Therefore, we have elected to use a
simpler morphologic classification. We acknowledge
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Posttransplantation Lymphoproliferative Disorders
267
TABLE 1. CLASSIFICATION SYSTEMS FOR LYMPHOPROLIFERATIVE DISORDERS OCCURRING AFTER TRANSPLANTATION
Genotypic*
Morphologic, Proposed by
Frizzera1
Simplified
Morphologic
lgH
EBV
c-myc
-
-
-
Polymorphic diffuse B-cell
hyperplasia
Polymorphic diffuse B-cell
lymphoma
Polymorphic PTLD
Immunoblastic sarcoma
Monomorphic PTLD
Usually responds spontaneously
+ 1 + 1
Typical reactive
hyperplasia
1 1+ +
Nonspecific reactive
hyperplasia
Empirical
-
+
+
+
Responds frequently to reduced
immunosuppression
Responds less frequently to
reduced immunosuppression
lgH = clonal immunoglobulin H gene rearrangement: EBV = clonal cpisomal Epstcin-Barr
virus genome: c-myc = c-myc rearrangement: PTLD = posttransplantation lymphoprolifera-
tive disorders: + = clonal gene rearrangement:
* Modified from Locker and Nalesnik.32
that transplant recipients develop typical follicular and/
or paracortical lymph node hyperplasia, and classify
atypical lymphoid hyperplasia as PTLD.1 This noncommital term was adopted to avoid implications in regard
to the neoplastic nature of a condition that defies such
assessment by histologic, immunophenotypic, or even
genetic probe analysis.829 Histomorphologic studies
yield only one distinction that may be of prognostic significance—specifically, monomorphism.1 Posttransplantation lymphoproliferative disorders composed of a
monomorphic population of immunoblasts is more
likely to progress despite a reduction in immunosuppression than is a polymorphic PTLD.1 Therefore we do not
advocate use of the classification proposed by Frizzera,
and recommend only two morphologic categories: polymorphic PTLD and monomorphic PTLD.1 The only
truly reliable predictor of good outcome, however, appears to be empirical—a favorable response to reduced
immunosuppression.1'7'8
In summary, transplant recipients may develop typical lymphoid hyperplasia that resembles that seen in
nonimmunocompromised patients and resolves spontaneously. Atypical lymphoid proliferations (PTLDs) often display microscopic features such as cellular atypia
and invasion which, if occurring in an immunocompetent patient, would be diagnostic of malignancy. In the
setting of reversible immunosuppression, however, the
diagnosis of malignant lymphoma should be avoided.
The polymorphous nature of PTLD is useful in distinguishing it from the infiltrate of small lymphocytes that
characterize rejection.
Many PTLDs display a polytypical mixture of lightchain expression by immunohistochemical analysis despite morphologic and clinical features that are suggestive of lymphoma.815 Southern-blot analysis for
immunoglobulin heavy- and light-chain gene rearrangement in PTLDs has revealed polyclonal, oligoclonal,
and monoclonal lesions,15 and even the presence of different individual clones in biopsy specimens taken from
different sites in the same patient.16'31 The method of
Activation/immortalization
of B cells by EBV
^ ,
FRV
*
* absence ofclonal gene rearrangement.
m
"
* *
*
QJL
Jfe
Apoptosis/immune cytolysis
Latent infection/immune
control of EBV infection
Maturation
Immunosuppression/loss
of immune control
Apoptosts/immune cytolysis
Genetic event
Oncogene activation/tumor
suppressor gene inactivation
»i*#
• • ! • •
• * • «
Ancillary Studies
Lymphoma in immunocompetent patients is invariably monoclonal, therefore immunophenotypic and genotypic analyses often are used to confirm the diagnosis.
Similar analysis has not proved as useful in PTLDs.
• • •
CTL a Cytotoxic T lymphocyte
* = EBV = Epstein-Barr virus
CsA o Cyclosporin A
FIG. 1. Hypothetical schema of the pathogenesis of posttransplantation
lymphoproliferative disorders.
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ANATOMIC PATHOLOGY
Review Article
FIG. 2. Section of lymph node from
an immunocompetent patient with
acute infectious mononucleosis
(case 1). There is effacement of the
architecture and extensive necrosis
(hematoxylin and eosin, original
magnification X250).
genotypic analysis is extremely sensitive and can detect
small monoclonal populations within even an extensive
polyclonal background. Therefore the results may not
correlate with immunohistochemical evidence for polyclonality.1517'25 The demonstration of neither immunoglobulin light-chain restriction8 nor clonal immunoglobulin gene rearrangement, however, accurately predicts
the patient response to therapy.1'21 Although polymorphic, polyclonal tumors appear to resolve more
frequently than monoclonal, monomorphic tumors,19'21'24'29 this observation is of limited value in the
treatment of an individual patient.6 Furthermore, the
lesion analyzed is not necessarily representative of lymphoid proliferation in other sites.16 A critical analysis of
FIG. 3. Perivascular clusters of viable lymphoid cells, including large
bizarre-appearing immunoblasts
resembling Reed-Sternberg cells in
case 1 (hematoxylin and eosin, original magnification X630).
#
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CRAIG, GULLEY, AND BANKS
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Posttransplantation Lymphoproliferative Disorders
FIG. 4. Polymorphous PTLD developing in a renal transplant recipient (case 2). There is a diffuse effacing polymorphous infiltrate of
lymphocytes, including immunoblasts, small cleaved cells, and
plasma cells. Several individual necrotic cellsand tingible body macrophages are present. No zones of necrosis are present (hematoxylin and
eosin, original magnification X250).
genotypic data by Locker and Nalesnik32 has revealed
several potential prognostic indicators. These authors
ascribed prognostic significance to the intensity of monoclonal bands identified by Southern-blot analysis.32 A
strong clonal band indicates a relatively large proportion
of cells from one clone and appears to correlate with
disease progression despite reduced immunosuppression. By contrast a weak band is less significant. The
clonality of PTLD also was demonstrated by structural
analysis of the episomal EBV DNA that is present in
virtually all cases.32 Employing this technique, PTLDs
with varying combinations of EBV and immunoglobulin heavy-chain gene clonality could be identified and
compared with their responses to reduced immunosuppressive therapy (Table 1). Although the demonstration
of clonal EBV DNA is one ofthe most sensitive methods
FIG. 5. Monoclonal, polymorphous PTLD developing in a renal
transplant recipient (case 3). Section of the submental lymph node
displaying effacement ofthe architecture by a diffuse, polymorphous
lymphocytic infiltrate. Numerous
tingible body macrophages impart
a "starry sky" appearance. There is
necrosis of individual cells but only
small geographic zones of necrosis
(hematoxylin and eosin, original
magnification X250).
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ANATOMIC PATHOLOGY
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FIG. 6. The infiltrate contains a
mixture of immunoblasts, small
cleaved cells, and plasma cells
(Case 3). A similar lymphoid infiltrate was identified in the salivary
gland (hematoxylin and eosin, original magnification X630).
for the detection of a monoclonal proliferation, its prognostic utility remains uncertain. The presence of a clone
of lymphocytes containing episomal EBV DNA may be
used to separate lymphadenopathy that requires treatment with reduced immunosuppression, i.e., PTLD,
from more typical, polyclonal, or EBV-negative lymph
node hyperplasia that may resolve spontaneously.
An association between disease progression and c-myc
oncogene rearrangement has been reported.32 Although
the latter observation may provide a clue about the
pathogenesis of PTLD and its progression to a true neoplasm, this rearrangement is found in too few cases to be
of diagnostic value. The response to an initial reduction
in immunosuppression still appears to be the most important indicator of outcome, and therefore immediate
assessment of such treatment should not be delayed in
deference to any of these ancillary studies.
nated with that of the normal tissues, and persists in the
same excessive manner after cessation of the stimuli
which evoked the change."33 Therefore, PTLD that progresses despite a clinical trial of reduced immunosuppression is probably best considered to be neoplastic, i.e.,
malignant lymphoma. In all other situations the term
PTLD is recommended.
The multiple factors involved in the pathogenesis of
PTLDs can be simplified into a three-step process that
leads to the development of neoplasia14 (Fig. 1). The first
step is the activation and immortalization of B lymphocytes by EBV. Step two is a progression of proliferation
due to immunosuppression. The resulting rapid and uncontrolled EBV-provoked proliferation greatly increases
the chance of a genetic event that irreversibly transforms
the lymphocytes into malignant cells (step 3). The mechanisms involved in these three steps follow.
PATHOGENESIS
Posttransplantation lymphoproliferative disorder includes a spectrum of EBV-related disorders ranging from
lymphoid hyperplasia to neoplasia. These disorders result from the interplay of multiple factors that can be
regarded as the multiple steps required for the production of a neoplasm. At what point should these proliferations be regarded as neoplastic? In this setting, clonality,
invasion, and metastasis are not useful criteria. An appropriate, albeit older, definition of neoplasia is "an abnormal mass of tissue which exceeds and is uncoordi-
Step 1
Epstein-Barr virus is a ubiquitous virus with a putative
role in the pathogenesis of Burkitt's lymphoma and nasopharyngeal carcinoma.18 Reactivation of latent EBV
infection, or less frequently, of primary EBV infection, is
strongly associated with the development of PTLD.34
Primary EBV infection is a productive, cytolytic infection.24 Latent infection appears to be a balance between
periodic viral shedding from the oral epithelium, secondary B-cell infection, and immune destruction of infected
cells by cytotoxic T lymphocytes.418'24 This balance can
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CRAIG, GULLEY, AND BANKS
Posttransplantation Lymphoproliferative Disorders
be disrupted by increased EBV-induced B-cell proliferation and by decreased immune destruction. The EBV
proteins, latent membrane-protein-1 and EBV nuclearantigen-2, are important in producing EBV-stimulated
B-cell proliferation and immortalization in vitro.35 These
proteins are strongly expressed in PTLD and may contribute to the lymphoid proliferation by up-regulating
the expression of the autocrine growth factor CD23.35
The expression of these genes also leads to the production of surface antigens, which in a nonimmunocompromised patient would stimulate T-cell cytotoxicity. By
contrast, the cells of Burkitt's lymphoma lack B-cell activation antigens (e.g., CD23), adhesion molecules, and
EBV-associated latent proteins (e.g., latent membraneprotein- 1 )52636and are therefore invisible to the immune
system. Despite the strong expression of surface antigens, the cells of PTLD continue to proliferate, unabated
by the immune system.
x
•«
S
r*
n
<s
Step 2
The similarity of PTLD to proliferations seen in other
acquired and congenital immunodeficiency syndromes,
and the regression of the disease after reduction in immunosuppressive therapy both support the central role of
immunodeficiency in the pathogenesis of this disorder.
The increased incidence of cancer in immunocompromised patients was initially attributed to decreased immune surveillance and impaired recognition and destruction of cancer cells.37 More recent theories, however,
center around the role of the immune system in the control of EBV infection.24 Although many immunosuppressive regimens are currently used, the incidence, interval
to onset, and nature of PTLD appear to be most dependent on the dose of CsA. This agent prevents allograft
rejection in a highly specific way by blocking the activation of alloreactive cytotoxic T lymphocytes through a
reduction in interleukin-2 production and interleukin-2
receptor expression. Cyclosporin A also inhibits the activation of EBV-specific cytotoxic T lymphocytes, which
confounds the patient's defense against EBV-induced Bcell proliferation.
In addition to cell lysis, EBV-infected lymphocytes die
by apoptosis. Apoptosis (programmed cell death) is a process of single cell death that involves intrinsic pathways
and appears to be independent of the viability of
surrounding cells. Apoptosis may, however, be induced
by an interaction with cytotoxic T lymphocytes.38 Single
cell death is a prominent feature of EBV infection in
immunocompetent hosts, and may be construed as a
self-sacrifice of infected cells. This process can be
disrupted by factors either extrinsic or intrinsic to the
cell. Intrinsic mechanisms include the EBV infection of
FIG. 7. Southern blot analysis performed on the lymph node (1) and
salivary gland (2) from case 3, revealing a monoclonal population of B
cells. Restriction enzymes used are indicated above each autoradiogram. Arrowheads indicate the germline bands, and lines indicate
clonal rearrangement of the immunoglobulin heavy-chain gene (JH
probe, Oncor, Gaithersburg, MD) with the enzymes HindlW and
BamHl. The clonal rearrangement is the same for the lymph node and
salivary gland. There was also clonal rearrangement of the kappa lightchain gene (Jkappa, Oncor Gaithersburg, MD) and absence of clonal
rearrangement of the T-cell receptor beta-chain gene (J/3 1 + 2 probe,
Oncor, Gaithersburg, MD).
B cells, a phenomenon associated with expression of the
protein bcl-2, which plays a role in preventing apoptosis.39 In addition, the EBV genome contains the gene
BHRF1, which has sequence homology with the bcl-2
gene and may therefore also inhibit apoptosis, leading to
B-cell immortalization.39 Cyclosporin A and EBV may
act synergistically to prevent the death of EBV-infected
lymphocytes. Cyclosporin A has been reported to induce
resistance of EBV-transformed B lymphocytes to immune cytolysis by blocking apoptosis.38 Therefore, although apoptosis may be seen in PTLD, relative suppression of this process may lead to an accumulation of
EBV-infected lymphocytes.
A similar accumulation of B cells could result from a
block in their maturation to plasma cells. Evidence for
Vol. 99 • No. 3
272
ANATOMIC PATHOLOGY
Review Arth
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FIG. 8. Southern blot autoradiograms indicating the presence of EBV DNA in the lymph node biopsy. The control EBV positive cell lines (Raji,
X50-7 and B95.8) are indicated. Left image. Bam HI -digested lymph node DNA from Case 3 probed with the EBV Ba/«HIW fragment. This probe
indicates the presence of EBV DNA by hybridizing with the 3.1-kb EBV BamHIW fragment. Cross-hybridization with the 1.8 kb-EBV BamHlY
fragment is indicated. Right image.fiamHI-digestedlymph node DNA from Case 3 probed with the Xho\a fragment of EBV that hybridizes with
the terminal region of the viral genome. A single band in the patient's sample indicates a monoclonal population of cells containing EBV DNA.
the latter mechanism includes the observation that regression of PTLD is accompanied by an apparent B-lymphocyte maturation with concomitant accumulation of
plasma cells.1
Step 3
The final step in oncogenesis probably involves the
activation of oncogenes or inactivation of tumor suppressor genes. Although translocation and subsequent
activation of the c-myc oncogene does not occur as frequently in PTLD as in Burkitt's lymphoma,20 c-myc
translocation has been associated with the development
of progressive PTLD unresponsive to immunosuppression reduction, i.e., the development of malignant lymphoma.32 Further investigation is required to determine
whether other oncogenes or tumor-suppressor genes are
involved in the progression of PTLD to unequivocal malignant lymphoma.
In summary, PTLD can be considered a defect in the
balance between cellular destruction (or maturation)
and cellular proliferation. Uncontrolled proliferation of
B lymphocytes enhances the likelihood of mutational
oncogenesis.
TREATMENT
Initially PTLD was assumed to be malignant lymphoma, and was treated as such with conventional chemotherapeutic regimens. This approach met with little
success.6,8"18 In recent years the emphasis has been on
the efficacy of reduction in immunosuppressive therapy.1,8 The success of this strategy indicates that many
PTLDs do not represent true neoplasms. Indeed, regression of both polymorphic, polyclonal lesions and monoclonal lesions has been well documented.1 Response to
therapy usually is seen within 2 weeks, and may occur
within a matter of days.1 In patients with monomorphic
and/or monoclonal lesions, some authors recommend
that a reduction in immunosuppressive therapy be combined with chemotherapy and/or radiation therapy.1'617
A short trial of reduced immunosuppressive therapy
alone, however, is usually acceptable. Patients with tumors localized at presentation or with residual localized
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CRAIG, GULLEY, AND BANKS
Posttransplantation Lymphoproliferative Disorders
273
FIG. 9. Polymorphous PTLD.
Lymph node section from case 4
displaying a polymorphous infiltrate of lymphoid cells that effaces
the architecture. Numerous mitotic
figures and areas of necrosis are
identified (hematoxylin and eosin,
original magnification X250).
tumor after a reduction in immunosuppressive therapy
may benefit from surgical resection.1,21
With reduced immunosuppressive therapy there is a
threat of allograft rejection. Loss of a renal homograft
can be managed by dialysis,6 and is therefore preferable
to the high mortality associated with uncontrolled
PTLD. Such a compromise strategy is not acceptable for
patients receiving less expendable homografts (e.g., cardiac or hepatic). Successful treatment of PTLD after
orthotopic liver transplantation has been achieved without rejection by using judicious reduction in immunosuppressive therapy.1
The value of antiviral agents in the treatment of PTLD
remains controversial. 619,21 In 1982 Hanto and colleagues described a patient with a polyclonal, polymorphic diffuse B-cell hyperplasia who appeared to respond
to acyclovir therapy alone.40 Acyclovir administration in
this case, however, was simultaneous with reduction in
immunosuppressive therapy. Acyclovir acts by preventing viral DNA synthesis, and hence viral replication and
shedding.41,42 This antiviral agent has no action against
circular, episomal EBV DNA contained within latently
infected lymphocytes. Although PTLD is most frequently associated with latent EBV infection, acyclovir
may be of value in preventing the ongoing infection of B
lymphocytes by virus shed from the oral epithelium.
This drug also may inhibit the replication of linear EBV
DNA sometimes identified within B lymphocytes containing circular latent viral particles.43 Although the effi-
cacy of acyclovir has not been proven, the low incidence
of complications associated with its administration has
led many groups to advocate its use in combination with
reduced immunosuppression. 1
CASE REPORTS
Case 1
An 18-year-old man presented in January 1986 with a 2-week history
of fever and headaches. On physical examination he was noted to have
an enlarged submandibular lymph node. Laboratory investigation revealed a white blood cell count of 20.6 X 109/L with 45% lymphocytes.
His symptoms persisted despite antibiotic therapy. A computed tomography scan revealed numerous enlarged thoracic and intraabdominal
lymph nodes and splenomegaly. A cervical lymph node biopsy was
performed (Figs. 2 and 3). Subsequent serologic studies revealed a positive Mono-latex (Wampole Laboratories, Cranbury, NJ) test. A diagnosis of infectious mononucleosis was made. In situ hybridization studies performed on paraffin-embedded tissue from this case revealed
EBV EBER1 small RNA gene expression in approximately 50% of the
small and large viable cells. The patient is well 7 years later.
This case illustrates some of the histologic changes associated with
acute EBV infection in an immunocompetent host. The presence of
extensive necrosis with large atypical immunoblasts is not a reliable
indicator of neoplastic transformation.*
Case 2
A 58-year-old woman received a cadaveric renal transplant in October 1987. The immunosuppression regimen included azathioprine,
* This case was kindly provided by Dr. Milka Montiel, University of
Texas Health Science Center at San Antonio, Texas.
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ANATOMIC PATHOLOGY
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FIG. 10. Polymorphous mixture of
immunoblasts, small cleaved cells,
and plasma cells from case 4 (hematoxylin and eosin, original magnification X630).
prednisolone, and CsA. Within 2 months fever, diffuse lymphadenopaCase 3
thy, and splenomegaly developed. A lymph node biopsy was perA 44-year-old man received a cadaveric renal transplant in October
formed, and revealed a polymorphous PTLD (Fig. 4). Immunohisto1991. The immunosuppressive regimen included azathioprine, CsA,
chemical studies performed on paraffin-embedded tissue revealed
and prednisolone. On the tenth day after transplantation he also repolyclonal staining for kappa and lambda immunoglobulin light
ceived
OKT3 for a suspected episode of rejection. Thirty-nine days
chains. A diagnosis of polyclonal, polymorphous B-cell hyperplasia
later "flulike" symptoms developed. The patient became febrile and
was made. The immunosuppression was reduced and acyclovir therapy
fullness developed in the neck region. A submandibular gland biopsy
commenced. The patient's subsequent course was complicated by
Staphylococcus aureus sepsis, bacterial thrombophlebitis, and dissemi- ' and submental lymph node resection were performed, and revealed a
monoclonal, polymorphous PTLD (Figs. 5-8).
nated intravascular coagulation. She died approximately 80 days after
The patient's lymphadenopathy resolved with a reduction in immutransplantation.
nosuppression
and acyclovir therapy. The renal allograft was rejected.
An autopsy examination revealed involvement of the liver, spleen,
This case illustrates the problems encountered in defining clonality
gastrointestinal tract, bladder, lung, renal allograft, and numerous
and the significance of thisfinding.Although paraffin-section immunolymph nodes by a polymorphous lymphoid infiltrate resembling that
histochemical studies showed a polyclonal pattern of immunoglobulin
seen in the lymph node biopsy. Southern-blot analysis of lymph node
light-chain staining, gene-probe analysis identified a clonal population
DNA procured at the time of autopsy revealed monoclonal rearrangeof lymphoid cells and a clone of cells containing EBV DNA. This case
ment of the immunoglobulin kappa light-chain gene. Autopsy examiis an example of a monoclonal lymphoid proliferation that resolved
nation also disclosed a pulmonary, necrotizing granuloma containing
with a reduction in immunosuppression.%
organisms with an appearance consistent with Hisloplasma capsulation.
This case demonstrates the rapid onset of generalized polymorphous
PTLD in a renal transplant recipient. Although the initial lymph node
Case 4
biopsy was polyclonal by immunophenotype, a genetic probe analysis
A 47-year-old man received a renal transplant in October 1991. Imperformed on the autopsy tissue revealed a monoclonal population of
munosuppressive therapy included azathioprine, prednisolone, and
lymphocytes. In situ hybridization studies revealed EBV EBER RNA
CsA. Because of an acute rejection episode the patient also received two
in 80% of the cells in this infiltrate. This casefitsthe original concept of
courses of OKT3. In January 1992, during the second course of OKT3
EBV-associated posttransplantation lymphoid proliferations with protherapy,
the patient developed peripheral and retroperitoneal lymphgression from a polyclonal to a fatal monoclonal disorder. Indicators of
adenopathy. Serum protein electrophoresis revealed a monoclonal
a poor prognosis include the generalized nature of the disorder and the
spike in the gamma region that was characterized as IgM/lambda. A
presence of associated pyogenic bacterial and fungal infections.f
lymph node biopsy was performed, and revealed a polymorphous
PTLD (Figs. 9 and 10).
•f This case was kindly provided by Dr. Askar Qalbani, Marian
Health Center, Sioux City, Iowa, and Dr. Fred Dick, University of Iowa
Medical Center, Iowa City, Iowa.
$ This case was kindly provided by Dr. John Metter, Humana Hospital-San Antonio, San Antonio, Texas.
AJ.C.P. • March 1993
CRAIG, GULLEY, AND BANKS
Posttransplantation Lymphoproliferative Disorders
275
FIG. 11. Immunohistochemical studies performed on paraffin-embedded tissue reveal a predominance of staining with primary antibodies directed
against lambda immunoglobulin light chain. Left image. Lambda light chain. Right image. Kappa light chain (original magnification X400).
Immunohistochemical studies and genetic-probe analysis performed
on the node revealed a monoclonal population of B lymphocytes (Fig.
11). Ten days later the patient underwent a partial small bowel resection for perforation. Examination of sections of the small bowel revealed an abnormal polymorphous infiltrate of immunoblasts and
plasma cells. In addition there were mucosal ulceration and fungal
organisms suggestive of Candida species. Immunosuppression was reduced, and acyclovir therapy was initiated. Despite rejection of the
kidney, the patient's condition improved and the lymphadenopathy
resolved. The quantity of the serum monoclonal spike also decreased.
This case is an example of PTLD presenting with diffuse lymphadenopathy and perforation of the gastrointestinal tract. Evidence of
monoclonality was provided by serum-protein electrophoresis, immunohistochemical staining, and gene-probe analysis performed on the
lymph node. Despite these indicators, which were suggestive of a poor
prognosis, the patient responded to decreased immunosuppression and
acyclovir administration^
CONCLUSION
After the original description in 1969 by Penn and
associates of the development of malignant lymphoma
in five renal transplant recipients,10 dramatic progress
has been made in the understanding of the pathogenesis
and treatment of PTLDs. These lymphoproliferative disorders have been recognized as being closely related to
those occurring in patients with inherited immunodefi-
§ This case was kindly provided by Dr. John Vago, The Christ Hospital, Cincinnati, Ohio.
ciency syndromes24 and in patients with the acquired
immunodeficiency syndrome.18 Immunodeficiency-associated lymphoid proliferations share many unusual
features, including a predilection for extranodal sites, a
varied morphologic appearance, a strong and probably
causal association with EBV infection, frequent absence
of immunophenotypic or genotypic evidence of monoclonality, and rapid progression with conventional chemotherapy and radiation therapy.20 The most distinctive
characteristic of the lymphoid proliferations occurring
in transplanted organ recipients is their ability to resolve
after diminished immunosuppression.8 It is essential
therefore that PTLDs be diagnosed early and treated appropriately. To achieve this, we recommend a simplified
morphologic classification of PTLD and an empiric approach to their treatment. In addition to their diagnostic
challenge, this fascinating group of iatrogenic disorders
may provide insight into the pathogenesis of lymphoid
neoplasia in general.
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