A 9-year-old female captive patas monkey (
Intravascular lymphoma (IVL) is a rare type of non-Hodgkin's lymphoma which is characterized by proliferation of neoplastic lymphocytes confined to blood vessel lumina in the absence of a primary extravascular tumor mass (Zuckerman et al., 2006; Ponzoni et al., 2007). In 1959, the entity was first described by Pfleger and Tappeiner as “angioendotheliomatosis proliferans systemisata”, referring to its suspected endothelial cell origin (Pfleger and Tappeiner, 1959). However, immunohistochemical investigations in the middle of the 1980s revealed the lymphocytic phenotype of the neoplastic cells, giving rise to reclassification of the neoplasm as “angiotropic large cell lymphoma” and “intravascular lymphomatosis” (Sheibani et al., 1986; Wick et al., 1986; Ferry et al., 1988). Apart from humans, IVL has been reported in a range of domestic animals, including dogs (Cullen et al., 2000; McDonough et al., 2002; Lane et al., 2012), cats (Lapointe et al., 1997; Henrich et al., 2007), and a horse (Raidal et al., 2006). Since the majority of cases in people are of B-cell origin with rare cases of T-cell and natural killer (NK)-cell tumors (Wick and Mills, 1991; Estalilla et al., 1999; Ferreri et al., 2004; Ponzoni and Ferreri, 2006; Zuckerman et al., 2006), only the B-cell IVL is listed in the World Health Organization classification of hematopoietic tumors, defining it as a rare variant of extranodal large B-cell lymphoma with selective intravascular growth (Nakamura et al., 2008). Cases in animals predominantly display a T-cell or a non-T-cell, non-B-cell phenotype (McDonough et al., 2002; Raidal et al., 2006). The clinical presentation of this systemic disease is diverse and depends on the spectrum of affected organs, rendering ante mortem diagnosis difficult (Ferreri et al., 2004; Zuckerman et al., 2006). Progressive occlusion of small vessels by neoplastic cells may result in thrombosis, hemorrhage, and infarction (Cullen et al., 2000; Bush et al., 2003). In humans, there is a clear relationship between T-cell IVL and Epstein–Barr virus (EBV, human herpes virus 4) infection, as demonstrated by detection of EBV RNA in lymphoma cells (Au et al., 1997; Cerroni et al., 2008).
In Old World monkeys, lymphomas are naturally occurring neoplasms. The vast majority of them are associated with certain viral agents (Bruce et al., 2012; Hirata et al., 2015; Hubbard et al., 1993; Hunt et al., 1983; Miller, 2012; Paramastri et al., 2002; Suzuki et al., 2005), whose natural host spectrum covers different African and Asian nonhuman primate species (Carville and Mansfield, 2008; Lerche and Osborn, 2003). In macaques, these agents include simian retroviruses, in particular simian immunodeficiency virus (SIV; Habis et al., 1999; Mätz-Rensing et al., 1999; Rivailler et al., 2004) and simian retrovirus (SRV) type D (Paramastri et al., 2002). In addition to the retrovirus-induced immunodeficiency, the development of lymphomas is thought to be associated with coinfection with one of two types of gammaherpesviruses, namely simian lymphocryptoviruses (LCVs), the simian equivalent of EBV (Blaschke et al., 2001; Bruce et al., 2012; Carville and Mansfield, 2008; Habis et al., 2000; Kahnt et al., 2002; Li et al., 1993; Mätz-Rensing et al., 1999; Pingel et al., 1997), and rhadinoviruses (Bruce et al., 2012; Orzechowska et al., 2008). In contrast to the aforementioned retroviruses, simian T-cell lymphotropic virus (STLV) associated lymphomagenesis in nonhuman primates does not seem to require a herpesviral co-infection (Allan et al., 2001; Homma et al., 1984; Hubbard et al., 1993).
In the present case report, we describe the clinical, morphological, and
immunophenotypical features of an IVL in a captive patas monkey
(
A 9-year-old female captive patas monkey (
Postmortem examination was performed according to a standard necropsy
protocol. Representative tissue samples were taken, fixed in 10 % neutral
buffered formalin, processed routinely, and embedded in paraffin wax.
Subsequently, 4
Tissue specimens from the brain were tested for a panel of viral agents known to be related to lymphomagenesis in monkeys by means of PCR. DNA was extracted using the DNA tissue kit (Qiagen, Hilden, Germany), and PCRs were performed for the detection of SIV (Clewley et al., 1998), simian T-cell leukemia virus type 1 (STLV-1; Leendertz et al., 2010), and herpes viruses, using pan-herpes primers (Chmielewicz et al., 2003). PCR products were purified using the Qiaquick PCR purification kit (Qiagen) and sequenced directly in both directions without interim cloning.
Upon gross examination, oligofocal red to dark brown areas ranging between 3 and 7 mm in diameter, consistent with infarctions, were detected in both cerebral hemispheres (Fig. 1). Moreover, multifocal petechial to ecchymotic hemorrhages were present in various organs (e.g., subcutis of the trunk, uterus, and urinary bladder). There was a mild serosanguinous pericardial effusion and mild splenomegaly. Inguinal and axillary lymph nodes were moderately enlarged, whereas visceral lymph nodes appeared normal.
Infarctions with hemorrhages (white arrows) in both cerebral hemispheres.
Cerebral capillaries distended by intravascular emboli of large
pleomorphic neoplastic lymphocytes. Adjacent cerebral parenchyma displays
loss of architecture, infiltration with numerous foamy macrophages,
lymphocytes, as well as hemosiderin and hematoidin deposition. H & E. Bar:
20
Histological examination revealed a lymphoproliferative process with a
striking restriction to blood vessel lumina. In the areas of cerebral
infarction (Fig. 2) as well as within meninges, prominent multifocal emboli
of large neoplastic lymphocytes within capillaries and small caliber venous
vessels were observed. Occasionally, affected vessels were markedly
distended by neoplastic cells (Fig. 2). The latter were characterized by
moderate anisocytosis and anisokaryosis showing moderate amounts of
homogenous to finely vacuolated amphophilic cytoplasm with distinct cellular
borders, irregularly round to polygonal nuclei with coarsely clumped
chromatin, and one to several variably distinct nucleoli. Mitotic figures
averaged four per high power field, occasionally displaying a bizarre
appearance. Upon careful screening, a corresponding intravascular neoplastic
cell population was found in a range of additional organs including
cerebellum (Fig. 3), spleen, mesenterial lymph nodes, bone marrow sinusoids,
ovary, haired skin, and intestine. Infrequently, infiltration of the
adjacent parenchyma by few neoplastic cells was observed within the cerebrum
and cerebellum, whereas no extravascular neoplastic mass could be detected.
While some of the occluded vessels within the cerebrum were associated with
extensive loss of architecture, hemorrhage, hemosiderin and hematoidin
deposition, as well as moderate histiocytic and lymphocytic infiltration of
the adjacent cerebral parenchyma, no secondary lesions were observed in the
other affected organs. In the liver and in the kidneys, a low-grade to
moderate multifocal inflammatory infiltrate was present, consisting of small
mature lymphocytes, and affecting hepatic sinusoids and portal triads as
well as renal interstitium respectively. The axillary and inguinal lymph
nodes displayed marked paracortical and low-grade to moderate follicular
hyperplasia. In the bone marrow moderate nodular lymphoid hyperplasia was
present. There was hematopoietic activity in all three lineages.
Immunohistochemically, the intravascular neoplastic cell population
virtually uniformly expressed CD3, characterized by a strong cytoplasmic
signal (Fig. 4), while it was negative for CD20, and CD68. There was no
evidence for expression of CD4 and CD8 in either tumor cells or normal
lymphoid tissue. Furthermore, 80–90 % of the neoplastic cells showed a
strong nuclear Ki-67 signal (Fig. 5). The hyperplastic lymphoid aggregates
in the bone marrow were predominantly composed of CD3
PCR amplification of tumor-bearing brain tissue yielded a strong signal for lymphocryptovirus. The sequences obtained were closely related to a previously published LCV-1 in a patas monkey (Ehlers et al., 2003). SIV and STLV-1 were not detected in tumor-bearing tissues by means of PCR.
Corresponding emboli of neoplastic lymphocytes distending multiple
capillaries within the cerebellum. The adjacent cerebellar parenchyma
appears normal. H & E. Bar: 20
Accumulation of large neoplastic lymphocytes filling the lumina of
multiple venules and capillaries within the ovary. Neoplastic cells show a
strong cytoplasmic CD3 expression. IHC, SABC method. Bar: 20
Venous vessel of a mesenterial lymph node with intravascular neoplastic lymphocytes highlighted by a
marked nuclear Ki-67 signal. IHC, SABC method. Bar: 20
Given the striking confinement of large neoplastic lymphocytes to vascular lumina without detection of an extravascular tumor mass and the uniform CD3 expression by neoplastic cells, an IVL of T-cell phenotype was diagnosed. In contrast to the present case, lymphomas in species closely related to the patas monkey, such as macaques and baboons, show a completely different morphology. They present as lymph node enlargements or distinct masses of viscera or diffuse infiltrations of organs and thus do not exclusively affect the vascular system (Bruce et al., 2012; Hirata et al., 2015; Hubbard et al., 1993; Hunt et al., 1983; Mätz-Rensing et al., 1999; Paramastri et al., 2002; Suzuki et al., 2005). Thus, to the authors' knowledge, this is the first report on an IVL in a nonhuman primate.
In humans, clinical presentation and organ involvement of IVL are diverse. In patients from Western countries, the skin and central nervous system (CNS) are commonly affected with corresponding neurological symptoms (Glass et al., 1993; Ferreri et al., 2004; Ponzoni et al., 2007), whereas cases in the Asian population are typically characterized by bone marrow involvement and thrombocytopenia (Murase et al., 2000). Neurological symptoms, such as circling, head tilt, and nystagmus reflecting brain or spinal cord involvement, are among the most common clinical features of IVL in dogs (McDonough et al., 2002; Zuckerman et al., 2006; Lane et al., 2012). However, in the case reported herein, clinical signs were rather nonspecific with only subtle neurological symptoms including ataxia. The latter may have been a result of impaired cerebellar perfusion due to occlusion of cerebellar blood vessels by neoplastic lymphocytes (Lane et al., 2012) and/or of circulatory disturbance due to poor general condition.
Laboratory findings are not specific but indicative for IVL (Ponzoni et al., 2007). The most consistent hematological abnormalities in both humans and animals include anaemia, thrombocytopenia, and leukopenia (McDonough et al., 2002; Ferreri et al., 2004; Henrich et al., 2007; Lane et al., 2012). While the former two abnormalities occurred in the present case, the patas monkey showed a marked leukocytosis instead of a leukopenia. This finding is in line with the observed lymphocytic hyperplasia of the bone marrow. Due to the diversity of clinical manifestation and the resulting lack of specific diagnostic parameters, final diagnosis of IVL is often not established until postmortem examination (McDonough et al., 2002; Ferreri et al., 2004; Zuckerman et al., 2006; Lane et al., 2012). This was also true for the present case.
Histopathologic characteristics of IVL in both humans and animals include
intravascular accumulation of large pleomorphic neoplastic lymphocytes in a
variety of organs with common involvement of the CNS. Infiltration of
adjacent parenchyma by neoplastic cells beyond endothelial lining is
observed infrequently (McDonough et al., 2002; Ferreri et al., 2004; Henrich et al., 2007). The reason for this almost
exclusive intravascular proliferation is poorly understood. In human B-cell
IVL, deficiencies of the lymphoma cells in
The T-cell origin of the neoplastic cells in the present case, as
demonstrated by CD3
In light of the clear association between T-cell IVL and EBV infection in people (Au et al., 1997; Cerroni et al., 2008) and a suspected connection of simian LCVs and non-Hodgkin's lymphomas in macaques (Pingel et al., 1997; Mätz-Rensing et al., 1999; Blaschke et al., 2001; Hirata et al., 2015; Kahnt et al., 2002; Rivailler et al., 2004; Carville and Mansfield, 2008), the molecular detection of LCV made us initially suspect a gammaherpesviral-induced lymphomagenesis in the present case. However, since we were not able to demonstrate LCV immunohistochemically within neoplastic cells, the role of the LCV in oncogenesis remains elusive, in particular because of the high prevalence of the virus in nonhuman primates (Bruce et al., 2012). Moreover, infections with retroviral agents known to occur in patas monkeys such as STLV and SIV (Bibollet-Ruche et al., 1996; Nerrienet et al., 2001) and with the potential to induce lymphoid hyperplasia, immunodeficiency, and lymphomas (Lerche and Osborn, 2003) could not be ruled out with certainty since a serum sample of the patas monkey was not available. However, SIV and STLV were not detected by means of PCR in tissue specimens of the monkey.
In conclusion, clinical and pathomorphological features of the reported case of IVL in a patas monkey are consistent with the characteristics of the entity in humans and domestic animals. This case is the first description of this rare neoplasia in a nonhuman primate and again illustrates the difficulty of ante mortem diagnosis of IVL. A virus-induced lymphomagenesis was initially suspected but could not be verified in the present case.
Underlying research data (histological slides) can be accessed upon request.
The authors declare that they have no conflict of interest.
The authors would like to express their cordial thanks to the head of the Pathology Unit of the German Primate Center, Franz-Josef Kaup, whose lifework this special issue is dedicated to. We gratefully acknowledge his encouraging support of collaborative scientific work and his critical review of the manuscript. Karen Lampe sincerely thanks F.-J. Kaup for the fascinating topic of her doctoral thesis he provided as well as for the opportunity of postgraduate training in the field of veterinary pathology. Moreover, we would like to thank Christina Perske, University Medical Center, Goettingen, for helpful discussion and advice concerning the case. The authors are also grateful to Larissa Hummel, Nadine Schminke, and Wolfgang Henkel from the Pathology Unit of the German Primate Center for excellent technical assistance. Edited by: E. Fuchs Reviewed by: two anonymous referees