Canine indolent and aggressive lymphoma: clinical spectrum with histologic correlation

Prognostic value of peripheral blood and bone marrow infiltration assessed by flow cytometry in dogs with de novo nodal peripheral T-cell lymphoma receiving alkylating-rich chemotherapy

Peripheral T-cell lymphoma (PTCL) is highly aggressive in dogs and demonstrates a poor response to traditional chemotherapy. The aim of this retrospective study was to assess the prognostic significance of peripheral blood (PB) and bone marrow (BM) infiltration evaluated by flow cytometry (FC) in dogs with treatment-naïve and histologically confirmed PTCL. To be included, dogs had to undergo complete staging, including FC on lymph nodes, PB and BM samples. Additionally, dogs had to receive an alkylating-rich protocol and have a complete follow-up. Treatment response was evaluated based on RECIST criteria at each chemotherapy session, and the end-staging was conducted at the completion of treatment. Endpoints were time to progression (TTP) and lymphoma-specific survival (LSS). The relationship between TTP/LSS and the percentage of PB and BM infiltration, categorized as > 1%, > 3%, > 5%, > 10%, > 15% and > 20% was investigated. Fifty dogs were included: based on imaging and FC, 78.0% had stage 5 disease, 14.0% had stage 4, 6.0% had stage 3 and 2.0% had stage 1. By multivariable analysis, the CD4-negative phenotype was the only factor associated with a shorter TTP (P = 0.049), while BM infiltration was significantly associated with LSS (P = 0.037). Dogs with BM infiltration > 5% had shorter median LSS (114 days; 95%CI: 0-240) compared to dogs with BM infiltration ≤ 5% (178 days; 95%CI: 145-211). Lack of complete response (P = 0.039) and administration of corticosteroids before chemotherapy (P = 0.026) also significantly worsened LSS. BM flow cytometric evaluation could be considered an essential part of staging work-up for dogs with PTCL and has prognostic relevance.

miRNome expression analysis in canine diffuse large B-cell lymphoma

Introduction

Lymphoma is a common canine cancer with translational relevance to human disease. Diffuse large B-cell lymphoma (DLBCL) is the most frequent subtype, contributing to almost fifty percent of clinically recognized lymphoma cases. Identifying new biomarkers capable of early diagnosis and monitoring DLBCL is crucial for enhancing remission rates. This research seeks to advance our knowledge of the molecular biology of DLBCL by analyzing the expression of microRNAs, which regulate gene expression by negatively impacting gene expression via targeted RNA degradation or translational repression. The stability and accessibility of microRNAs make them appropriate biomarkers for the diagnosis, prognosis, and monitoring of diseases.

Methods

We extracted and sequenced microRNAs from ten fresh-frozen lymph node tissue samples (six DLBCL and four non-neoplastic).

Results

Small RNA sequencing data analysis revealed 35 differently expressed miRNAs (DEMs) compared to controls. RT-qPCR confirmed that 23/35 DEMs in DLBCL were significantly upregulated (n = 14) or downregulated (n = 9). Statistical significance was determined by comparing each miRNA's average expression fold-change (2-Cq) between the DLCBL and healthy groups by applying the unpaired parametric Welch's 2-sample t-test and false discovery rate (FDR). The predicted target genes of the DEMs were mainly enriched in the PI3K-Akt-MAPK pathway.

Discussion

Our data point to the potential value of miRNA signatures as diagnostic biomarkers and serve as a guideline for subsequent experimental studies to determine the targets and functions of these altered miRNAs in canine DLBCL.

Review of Canine Lymphoma Treated with Chemotherapy-Outcomes and Prognostic Factors

While canine lymphoma is a relatively common and important disease seen by veterinarians, there are limited comprehensive reviews of the literature regarding the remission and survival times following chemotherapy, and the associated prognostic factors. This comprehensive thematic review covers the available veterinary literature covering treatment outcomes and identified prognostic factors. A lack of standardised approaches to evaluate and report the outcomes was identified, including factors that would alter the duration of responses by weeks, or occasionally months. After publication of the suggested reporting criteria, this has improved but is still not uniformly applied. The prognostic factors included for evaluation varied from as few as three to seventeen, with over 50 studies using only univariate analysis. Individual papers reported much longer outcomes than others, but assessing the outcomes overall, there has been minimal change over the last 40 years. This supports the belief that novel approaches for lymphoma therapy will be required to substantively improve outcomes.

Age at cancer diagnosis by breed, weight, sex, and cancer type in a cohort of more than 3,000 dogs: Determining the optimal age to initiate cancer screening in canine patients

The goal of cancer screening is to detect disease at an early stage when treatment may be more effective. Cancer screening in dogs has relied upon annual physical examinations and routine laboratory tests, which are largely inadequate for detecting preclinical disease. With the introduction of non-invasive liquid biopsy cancer detection methods, the discussion is shifting from how to screen dogs for cancer to when to screen dogs for cancer. To address this question, we analyzed data from 3,452 cancer-diagnosed dogs to determine the age at which dogs of certain breeds and weights are typically diagnosed with cancer. In our study population, the median age at cancer diagnosis was 8.8 years, with males diagnosed at younger ages than females, and neutered dogs diagnosed at significantly later ages than intact dogs. Overall, weight was inversely correlated with age at cancer diagnosis, and purebred dogs were diagnosed at significantly younger ages than mixed-breed dogs. For breeds represented by ≥10 dogs, a breed-based median age at diagnosis was calculated. A weight-based linear regression model was developed to predict the median age at diagnosis for breeds represented by ≤10 dogs and for mixed-breed dogs. Our findings, combined with findings from previous studies which established a long duration of the preclinical phase of cancer development in dogs, suggest that it might be reasonable to consider annual cancer screening starting 2 years prior to the median age at cancer diagnosis for dogs of similar breed or weight. This logic would support a general recommendation to start cancer screening for all dogs at the age of 7, and as early as age 4 for breeds with a lower median age at cancer diagnosis, in order to increase the likelihood of early detection and treatment.

Randomised trial evaluating chemotherapy alone or chemotherapy and a novel monoclonal antibody for canine T-cell lymphoma: A multicentre US study

Background

Canine peripheral nodal T‐cell lymphoma is considered chemotherapy resistant and carries a relatively poor prognosis. Prospective evaluations reporting the impact of chemotherapy on progression‐free survival (PFS) and overall survival time for dogs with T‐cell lymphoma are lacking. This study examined the impact of L‐CHOP (L‐asparaginase, doxorubicin, cyclophosphamide, vincristine, prednisone) chemotherapy or L‐CHOP in combination with AT‐005, a US Department of Agriculture‐licensed caninised monoclonal antibody, on PFS and response rates in dogs with clinical intermediate‐ and high‐grade peripheral nodal T‐cell lymphoma.

Methods

A prospective, randomised, placebo‐controlled, investigator‐ and owner‐blinded, multicentre study was completed. All dogs received a 19‐week L‐CHOP chemotherapy protocol with randomisation (1:1) into placebo or AT‐005 groups. Response was evaluated via the Veterinary Cooperative Oncology Group criteria for canine lymphoma.

Results

Forty‐nine dogs were enrolled (25 received placebo and 24 received AT‐005). Most demographic factors were similar between the two groups, with the exception that more dogs with stage IV and V disease were treated with AT‐005 (34% vs. 8%; p = 0.03). Median PFS was 103 days (95% confidence interval [CI], 56–118) in the placebo group versus 64 days (95% CI, 36–118) in the AT‐005 group. The overall response rate (ORR) for all dogs was 98% (48 of 49); complete response rate in the placebo group (64%) was not different from the AT‐005 group (67%).

Conclusions

To the best of the authors’ knowledge, this is the first prospective study to document that treatment with L‐CHOP chemotherapy, with or without AT‐005, may result in a high ORR, but relatively brief PFS in dogs with clinical intermediate‐ and high‐grade T‐cell lymphoma.

Clinical outcome and Ki67 evaluation in dogs with nodal small cell B-cell lymphoma diagnosed by flow cytometry

Background

Nodal small cell B‐cell lymphoma subtypes in dogs cannot be distinguished by flow cytometry and information regarding treatment, prognosis, and outcome are limited.

Hypothesis/Objectives

Objectives were to describe outcome in dogs with nodal small cell B‐cell lymphoma diagnosed by flow cytometry and correlate clinical and laboratory data with survival. We hypothesized that B‐cell Ki67 expression measured by flow cytometry is associated with shorter progression free survival (PFS) and overall survival (OS).

Animals

Forty‐nine dogs with nodal small cell B‐cell lymphoma, defined by >80% CD21+ B‐cells by flow cytometry and small‐sized B‐cells by forward scatter.

Methods

Retrospective study reviewing treatment and outcome data extracted from medical records. Percentage of Ki67‐expressing B‐cells was measured by flow cytometry. Clinical, laboratory, and flow cytometry data were assessed for association with outcome.

Results

Median percentage of B‐cell Ki67 was 41% (range, 3%‐97%). Median PFS was 119 days and median OS was 222 days (n = 49). Among cases treated with CHOP‐based chemotherapy (n = 32), median PFS was 70 days, median OS was 267 days, and 50% of cases achieved complete response. Low percentage of B‐cell Ki67 (≤11%) was associated with prolonged OS by univariable analysis. Greater age, substage B, high B‐cell CD25 expression and low B‐cell CD21 and class II major histocompatibility complex expression by flow cytometry were independently associated with shorter OS.

Conclusions and Clinical Importance

Most nodal small cell B‐cell lymphoma cases had aggressive disease. Low Ki67 expression can help identify cases with better prognosis. Age, substage, and flow cytometry variables are useful prognostic factors.

Diffuse large B cell lymphoma and a novel gammaherpesvirus in northern elephant seals Mirounga angustirostris

Two emaciated male northern elephant seal (NES) Mirounga angustirostris pups were admitted to The Marine Mammal Center (Sausalito, California, USA) and treated for malnutrition. Complete blood counts showed a progressive moderate to marked leukocytosis characterized by a predominance of large monomorphic mononuclear cells of probable lymphoid origin, frequently with flower-shaped nuclei. Both seals were euthanized due to suspected lymphoid neoplasia. At necropsy, most lymph nodes in both pups were markedly enlarged, some with distinct white nodules, the spleens were diffusely enlarged, and the intestinal mucosae were thickened. Histopathologic features consistent with disseminated large cell lymphoma were identified to varying degrees of severity in lymph nodes, bone marrow, liver, tonsils, spleen, liver, intestines, kidneys, lower urinary tract, and several other organs. Immunohistochemical staining of neoplastic cells was most consistent with B lymphocyte origin, with most cells staining positively for Pax 5 and CD20 with admixed small CD3-positive T lymphocytes and CD204-positive macrophages. PCR and sequencing identified a novel gammaherpesvirus, herein called miroungine gammaherpesvirus 3, from affected tissues. This virus is in a clade outside of named genera that utilize hosts in the suborder Caniformia. The present study is the first description of diffuse large B cell lymphoma with leukemic manifestation and concomitant detection of a novel gammaherpesvirus in free-living NESs. Further research regarding the prevalence of this new gammaherpesvirus and its associated pathogenesis in this species is indicated.

Clinical and Clinical Pathological Presentation of 310 Dogs Affected by Lymphoma with Aberrant Antigen Expression Identified via Flow Cytometry

Phenotypic aberrancies have been reported occasionally in canine lymphomas. Here, we retrospectively collected 310 canine lymphomas with an aberrant phenotype detected via flow cytometry and describe their clinical and clinical pathological features at diagnosis. There were 152 T-cell lymphomas not otherwise specified (T-NOS), 101 T-zone lymphomas (TZL), 54 B-cell lymphomas, and 3 cases with two suspected concurrent neoplastic populations. The most represented aberrancies were: CD5-, CD4-CD8-, and CD3- in T-NOS lymphomas, CD21+, CD4-CD8-, and CD3- in TZLs, and CD34+, CD44-, and CD5+ in B-cell lymphomas. Among T-cell lymphomas, the aberrant expression of CD21 was significantly more frequent in TZL and the loss of CD5 and CD44 in T-NOS. More than 75% of dogs were purebred; males outnumbered females; the mean age at diagnosis was 8–10 years, depending on lymphoma subtype. A few dogs were symptomatic at the time of diagnosis, and 30% had peripheral blood abnormalities, in line with what is already reported for the general population of dogs with lymphoma. Further studies are needed to assess the pathogenetic mechanisms underlying each specific antigen aberrancy, as well as the diagnostic and prognostic role.

Performance of lymph node cytopathology in diagnosis and characterization of lymphoma in dogs

BACKGROUND

Cytopathology is a minimally invasive and convenient diagnostic procedure, often used as a substitute for histopathology to diagnose and characterize lymphoma in dogs.

OBJECTIVES

Assess the diagnostic performance of cytopathology in diagnosing lymphoma and its histopathological subtypes in dogs.

ANIMALS

One-hundred and sixty-one lymph node samples from 139 dogs with enlarged peripheral lymph nodes.

METHODS

Based only on cytopathology, 6 examiners independently provided the following interpretations on each sample: (a) lymphoma vs nonlymphoma; (b) grade and phenotype; and (c) World Health Organization (WHO) histopathological subtype. Histopathology and immunohistochemistry (IHC) findings were used as reference standards to evaluate diagnostic performance of cytopathology. Clinical, clinicopathologic, and imaging data also were considered in the definitive diagnosis.

RESULTS

Classification accuracy for lymphoma consistently was >80% for all examiners, whereas it was >60% for low grade T-cell lymphomas, >30% for high grade B-cell lymphomas, >20% for high grade T-cell lymphomas, and <40% for low grade B-cell lymphomas. Interobserver agreement evaluated by kappa scores was 0.55 and 0.32 for identification of lymphoma cases, and of grade plus immunophenotype, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Cytopathology may result in accurate diagnosis of lymphoma, but accuracy decreases when further characterization is needed. Cytopathology represents a fundamental aid in identifying lymphoma and can be used as a screening test to predict grade and phenotype. However, these results must be confirmed using other ancillary techniques, including flow cytometry, histopathology, and immunohistochemistry (IHC).

Maintenance treatment in relapsed canine lymphoma after a short L-CHOP protocol

OBJECTIVE

A number of different rescue protocols for relapsed canine multicentric large-cell lymphoma have been described. The aim of this pilot study was to evaluate the efficacy of a maintenance treatment in dogs that experienced a second complete remission after a short L-CHOP-rescue protocol.

MATERIAL AND METHODS

Included in the study were dogs experiencing the first lymphoma relapse during a treatment-free period which were treated with a short L-CHOP protocol, achieved a complete remission and were afterwards treated with a continuous maintenance phase (MP) protocol. The L-CHOP protocol consisted of weekly treatments, with at least 3 additional treatments following complete remission. Thereafter the MP protocol with 2-week treatment intervals was conducted. It consisted of alternating oral home administration of different alkylating agents and one intravenously administered cytotoxic agent of a different mechanism of action. The dogs were presented either every 4 or 6 weeks for intravenous treatment and at this time a complete blood count was performed. The durations of the first remission, disease-free interval and overall survival time were evaluated.

RESULTS

A total of 20 dogs were included in the study. A median of 7 weekly applications were given before the treatment was switched to the MP protocol. During MP, 14 dogs were treated intravenously every 6 weeks and 6 dogs every 4 weeks. Haematological adverse events were mainly mild. During the L-CHOP-protocol, one septic event occurred, and 2 dogs were hospitalized due to gastrointestinal adverse events. No patient required hospitalization during the MP. Fifteen dogs completed at least one cycle in the MP and a median of 8.5 chemotherapeutic treatments were administered. The median disease-free interval was 264 days and the median overall survival time was 737 days.

CONCLUSION AND CLINICAL RELEVANCE

The protocol was generally well tolerated. Since 5 patients showed disease progression during the first cycle of the MP, dogs should ideally be evaluated for minimal residual disease before being switched to the MP. The case number in the presented study was low and the treatment relatively heterogeneous. Therefore, more dogs have to be treated with the proposed protocol before general recommendations can be made.

Evaluation of the Proliferative Activity of Diffuse Large B-Cell Lymphoma (DLBCL) in Dogs with Respect to Patient Eligibility for Anthracycline-Based Chemotherapy

Simple Summary

Canine lymphomas usually have aggressive behavior, but respond well to chemotherapy. Despite proper diagnosis and numerous available therapeutic regimens, it is difficult to determine the prognosis and choose the optimal method of treatment in each individual patient. Diffuse large B-cell lymphoma is the most commonly diagnosed histological subtype of canine lymphoma and is treated with anthracyclines alone or in combination with other chemotherapeutics. A new diagnostic marker of prognostic and predictive value is topoisomerase IIα, which also constitutes a molecular target for anti-cancer drugs belonging to the group of topoisomerase IIα inhibitors including anthracyclines. Proliferative activity was estimated in samples of enlarged lymph nodes in dogs with diffuse large B-cell lymphoma based on mitotic count and immunohistochemical evaluation of topoisomerase IIα and Ki67 antigen expression with a view to qualifying patients for anthracycline-base chemotherapy. It has been shown that higher levels of topoisomerase IIα expression corresponded to a higher mitotic count but not to Ki67 index. These results indicate that an immunohistochemical evaluation of topoisomerase IIα expression can be used to develop a diagnostic-clinical protocol for the treatment of dogs with diffuse large B-cell lymphoma using anthracycline-based chemotherapy.

Abstract

Different types of canine lymphoma respond differently to chemotherapy and have different prognoses. Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma in dogs. Topoisomerase II alpha (TOPIIα) protein has been shown to be a proliferation marker associated with prognostic significance. The aim of the study was to determine the relationship between TOPIIα expression, mitotic count (MC), and Ki67 antigen index in DLBCL in dogs, taking into account the applicability of these parameters to select the chemotherapy protocol with emphasis on the use of anthracycline drugs. Samples of formalin-fixed paraffin-embedded lymph nodes from 34 dogs with DLBCL were immunohistochemically labelled with anti-TOPIIα and Ki67. The number of positive cells and the intensity of the reaction were taken into account in order to assess TOPIIα expression. MC was estimated in the hematoxylin and eosin-stained slides in the area of 2.37 mm². Positive association between TOPIIα and MC, but no association between TOPIIα and Ki67 was found. It can be concluded that the immunohistochemical determination of TOPIIα as a molecular target for drugs from the anthracycline group may be used in association with MC to establish a diagnostic-clinical protocol for selecting dogs with DLBCL for treatment with anthracycline drugs.

Phenotypical Characterization and Clinical Outcome of Canine Burkitt-Like Lymphoma

In dogs, Burkitt-like lymphoma (B-LL) is rare tumor and it is classified as a high-grade B-cell malignancy. The diagnosis is challenging because of the similar histologic appearance with other histotypes, no defined phenotypical criteria and poorly described clinical aspects. The aim of the study was to provide a detailed description of clinical and morphological features, as well as immunophenotypical profile of B-LL in comparison with the human counterpart. Thirteen dogs with histologically proven B-LL, for which a complete staging and follow-up were available, were retrospectively selected. Immunohistochemical expression of CD20, PAX5, CD3, CD10, BCL2, BCL6, MYC, and caspase-3 was evaluated. Histologically, all B-LLs showed a diffuse architecture with medium to large-sized cells, high mitotic rate and diffuse starry sky appearance. B-phenotype of neoplastic cells was confirmed both by flow-cytometry and immunohistochemistry. Conversely, B-LLs were negative for BCL2 and MYC, whereas some cases co-expressed BCL6 and CD10, suggesting a germinal center B-cell origin. Disease stage was advanced in the majority of cases. All dogs received CHOP-based chemotherapy with or without immunotherapy. Despite treatment, prognosis was poor, with a median time to progression and survival of 130 and 228 days, respectively. Nevertheless, ~30% of dogs survived more than 1 year. An increased apoptotic index, a high turnover index and caspase-3 index correlated with shorter survival. In conclusion, canine B-LL shows phenotypical differences with the human counterpart along with features that might help to differentiate this entity from diffuse large B-cell lymphoma.

Canine lymphoma and vector-borne diseases: Molecular and serological evaluation of a possible complicity

Lymphoma is the most common haematological malignancy in dogs and its aetiology is largely unknown. The presence of canine vector-borne agents (CVBD) in lymphoma tissues has been described and its causative effects questioned. We intended to evaluate the presence and extent of Leishmania infantum, Ehrlichia canis, Anaplasma phagocytophilum and Bartonella henselae infection in dogs with lymphoma. Sixty-one dogs, living in the Lisbon metropolitan area, with a diagnosis of lymphoma were enrolled. Immunofluorescence assays were used to detect serum IgG's. The presence of DNA from CVBD agents in tumour tissue was assessed by PCR. All dogs tested negative for B. henselae, A. phagocytophilum and E. canis by both serology and PCR. Regarding L. infantum, 8.2% (n = 5) of the dogs had a positive serologic result. L. infantum DNA was detected in two samples of diffuse large B-cell lymphoma (DLBCL). These results show an increased, but not significant, seropositivity (8.2% vs 7.9%) and molecular detection (3.3% vs 1.2%) for L. infantum in dogs with lymphoma, when compared to the reported canine population in the same geographical area. We could not identify an association between lymphoma and E. canis, A. phagocytophilum, B. henselae or Leishmania infantum infection in the studied population. Nevertheless, further studies, following dogs trough their CVBD disease evolution, are worthwhile and may help clarify a possible role of CVBD agents in lymphomagenesis.

Variation of apoptotic and proliferative activity among lymphoma subtypes in dogs: A flow cytometric study

Tumor growth depends on both proliferative and apoptotic rate of neoplastic cells. High proliferation index is a well-known negative prognostic factor in canine lymphomas, whereas little is known about apoptotic activity. We describe proliferative and apoptotic rates in different canine lymphoma subtypes at diagnosis. Flow cytometry (FC) was used to assess the percentage of proliferating cells (Ki67%) and of apoptotic cells (AnnV%) in 128 lymph node (LN) aspirates from dogs with lymphoma. Proliferation/apoptosis ratio (PAR) and turnover index (TI; Ki67% + AnnV%) were then calculated for each case. High-grade B-cell lymphomas showed high values for both Ki67% and AnnV%, low-grade B-cell lymphomas showed low Ki67% and high AnnV%, high-grade T-cell lymphomas showed high Ki67% and low AnnV%, and low-grade T-cell lymphomas showed low levels of both parameters. Lymphoblastic lymphomas had the highest PAR values. High-grade B-cell lymphomas had the highest TI values while small clear cells lymphomas the lowest. The panorama of proliferative and apoptotic activity widely varies among lymphoma subtypes. Our results lay the ground for future clinical and pharmacological studies.

CD3-CD20-positive nodal lymphoma with cross-lineage rearrangement in a dog

A 7-y-old mixed-breed male dog was presented with a history of generalized lymphadenopathy. Fine-needle aspirates of the enlarged peripheral lymph nodes were suggestive of lymphoma. Histologic examination of a retromandibular lymph node was suggestive of high-grade, medium large-cell lymphoma. Immunohistochemistry revealed concurrent expression of CD3 and CD20. The co-localization of the 2 antigens was confirmed by immunofluorescence. PCR for antigen receptor gene rearrangements (PARR) detected clonal rearrangements for both T-cell receptor gamma and B-cell receptor. The final diagnosis was CD3-CD20-positive anaplastic lymphoma with cross-lineage rearrangement.

Long-Term Observation of the Progression From Nodal Marginal Zone Lymphoma to Diffuse Large B-Cell Lymphoma in a Dog

A 4-year and 10-month old female Pembroke Welsh Corgi presented with an enlarged right popliteal lymph node, and a histopathological diagnosis of nodal marginal zone lymphoma (nMZL) was made. After resection of the lymph node, follow-up observation was continued without chemotherapy. At 22 months after initial presentation, the dog developed enlargement of peripheral lymph nodes, and the histopathological diagnosis was late-stage nMZL. Multidrug chemotherapy induced clinical complete remission, but the tumor relapsed with enlargement of peripheral and abdominal lymph nodes 42 months after initial presentation. Second-round multidrug chemotherapy induced complete clinical remission again; however, the tumor relapsed with lymphadenopathy 47 months after initial presentation. The dog died 59 months after initial presentation, and postmortem examination revealed generalized lymphadenopathy; the histopathological diagnosis was diffuse large B-cell lymphoma (DLBCL). Polymerase chain reaction for antigen receptor gene rearrangements revealed that the nMZL and DLBCL samples were derived from the same B-lymphocyte clone.

Integrated analysis of transcriptome, methylome and copy number aberrations data of marginal zone lymphoma and follicular lymphoma in dog

Marginal zone lymphoma (MZL) and follicular lymphoma (FL) are classified as indolent B-cell lymphomas in dogs. Aside from the clinical and histopathological similarities with the human counterpart, the molecular pathogenesis remains unclear. We integrated transcriptome, genome-wide DNA methylation and copy number aberration analysis to provide insights on the pathogenesis of canine MZL (n = 5) and FL (n = 7), also comparing them with diffuse large B-cell lymphoma (DLBCL). Transcriptome profiling highlighted the presence of similar biological processes affecting both histotypes, including BCR and TLR signalling pathways. However, FLs showed an enrichment of E2F targets, whereas MZLs were characterized by MYC-driven transcriptional activation signatures. FLs showed a distinctive loss on chr1 containing CEACAM23 and 24, conversely MZLs presented multiple recurrent gains on chr13, where MYC is located. The distribution of methylation peaks was similar between the two histotypes. Integrating data from the three omics, FLs resulted clearly separated from MZLs and DLBCL dataset. MZLs showed the enrichment of FoxM1 network and TLR associated TICAM1-dependent IRFs activation pathway. However, no specific signatures differentiated MZLs from DLBCLs. In conclusion, our study presents the first comprehensive analysis of molecular and epigenetic pathogenesis of canine FL and MZL.

Diagnosis of canine renal lymphoma by cytology and flow cytometry of the urine

Lymphoma is a common hematopoietic neoplasm of dogs. A definitive diagnosis typically requires the collection of samples via fine-needle aspirate or biopsy. A unique case of canine renal T-cell lymphoma diagnosed using urine sediment microscopy with flow cytometry and PCR for Antigen Receptor Rearrangement (PARR) is presented. A fresh urine sample was collected via a urinary catheter and immediately prepared for cytologic examination, flow cytometry, and PARR. The flow cytometric study revealed that 83% of the cells were large CD3⁺ CD8⁺ T cells, while PARR identified a clonally rearranged T-cell receptor gene, supporting the flow cytometry findings. Despite supportive care, the patient progressed to anuric renal failure and was humanely euthanized. A necropsy was performed, and tissues from the upper and lower urinary tracts were collected. Histologically, the right and left kidneys were infiltrated by a neoplastic round cell population effacing the cortex and medulla. Immunohistochemistry for the T- and B-cell antigens CD3 and CD20, respectively, revealed that the neoplastic population within the kidney demonstrated diffuse, strong, membranous to intracytoplasmic CD3 expression while lacking CD20 expression. These results confirmed the diagnosis of renal T-cell lymphoma. This is the first known report of canine lymphoma diagnosed using either urine flow cytometry or clonality testing. Therefore, in select cases, urine flow cytometry and/or PARR are feasible to perform on urine-derived cells as a quick and cost-effective means to aid in the diagnosis of urinary tract lymphoma.

Prospective evaluation of flow cytometric characteristics, histopathologic diagnosis and clinical outcome in dogs with naïve B-cell lymphoma treated with a 19-week CHOP protocol

Canine B-cell lymphoma is a clinically heterogenous disease; however, it is generally treated as a single disease entity. The purpose of this clinical trial was to prospectively evaluate naïve canine B-cell lymphoma patients using histopathology, flow cytometry (FC) and a standardized chemotherapy protocol to better define subsets of this disease that may respond differently to treatment. Sixty-four dogs with naïve multicentric B-cell lymphoma were treated with a standardized 19-week CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy protocol. Most of the dogs (84.3%) were diagnosed with diffuse large B-cell lymphoma (DLBCL), followed by nodal marginal zone (7.8%), small B-cell (4.7%), Burkitt-like (1.6%) and follicular lymphoma (1.6%). FC confirmed the diagnosis of B-cell lymphoma in all cases. There were no clear phenotyping differences between the subtypes of B-cell lymphoma detectable by our FC panel. The histologic subtypes in this study exhibited a range of forward scatter values on flow cytometry, but all of the DLBCL cases were higher than a value of 469, while the only cases with a lower forward scatter value were follicular lymphoma and diffuse small B-cell lymphoma. Dogs with DLBCL had a significantly better objective response rate to the CHOP protocol (96.3%) than the non-DLBCL subtypes (70%, P = .024). The median progression-free survival time for patients with DLBCL (233 days) was significantly longer than that of all other histopathologic subgroups combined (163 days, P = .0005).

Epidemiology, clinical and cytological features of lymphoma in Boxer dogs

The aim of this study was to evaluate the epidemiology, clinical and laboratory characteristics of canine lymphomas as well as some aspects of treatment outcomes. The study was conducted on Boxer dogs with lymphoma diagnosed by cytology and immunocytochemistry (CD3 and CD79 alpha). During the study period, lymphoma was diagnosed in 63 Boxers; 86.8% were T-cell (based on the Kiel classification: small clear cell lymphoma, pleomorphic small cell lymphoma, pleomorphic mixed T-cell lymphoma, pleomorphic large T-cell lymphoma, lymphoblastic lymphoma/acute lymphoblastic leukaemia) and 13.2% were B-cell lymphomas (according to the Kiel classification: B-cell chronic lymphocytic leukaemia, centroblastic/centroblastic polymorphic lymphoma). Overall survival (OS) was significantly longer in dogs with low-grade than with high-grade lymphoma (median OS of 6.8 and 4.7 months, respectively; P = 0.024). OS was not influenced by WHO clinical stage, WHO clinical substage, presence of splenomegaly, early administration of glucocorticoids or the time from the first presentation to the beginning of chemotherapy. There are no significant differences in clinical and laboratory parameters between low-grade and high-grade lymphomas. Boxer dogs are predisposed to T-cell lymphoma, with a predominance of high-grade tumour, especially pleomorphic, mixed small and large T-cell subtype. It is possible that Boxer dogs may respond less favourably to chemotherapy than patients of other breeds.

Mutational landscape of canine B-cell lymphoma profiled at single nucleotide resolution by RNA-seq

The genomic landscape in human B-cell lymphoma has revealed several somatic mutations and potentially relevant germline alterations affecting therapy and prognosis. Also, mutations originally described as somatic aberrations have been shown to confer cancer predisposition when occurring in the germline. The relevance of mutations in canine B-cell lymphoma is scarcely known and gene expression profiling has shown similar molecular signatures among different B-cell histotypes, suggesting other biological mechanisms underlining differences. Here, we present a highly accurate approach to identify single nucleotide variants (SNVs) in RNA-seq data obtained from 62 completely staged canine B-cell lymphomas and 11 normal B-cells used as controls. A customized variant discovery pipeline was applied and SNVs were found in tumors and differentiated for histotype. A number of known and not previously identified SNVs were significantly associated to MAPK signaling pathway, negative regulation of apoptotic process and cell death, B-cell activation, NF-kB and JAK-STAT signaling. Interestingly, no significant genetic fingerprints were found separating diffuse large B-cell lymphoma from indolent lymphomas suggesting that differences of genetic landscape are not the pivotal causative factor of indolent behavior. We also detected several variants in expressed regions of canine B-cell lymphoma and identified SNVs having a direct impact on genes. Using this brand-new approach the consequence of a gene variant is directly associated to expression. Further investigations are in progress to deeply elucidate the mechanisms by which altered genes pathways may drive lymphomagenesis and a higher number of cases is also demanded to confirm this evidence.

Prognostic significance of peripheral blood and bone marrow infiltration in newly-diagnosed canine nodal marginal zone lymphoma

Canine nodal marginal zone lymphoma (nMZL) is infrequent and is typically diagnosed at an advanced disease stage. However, it is currently unknown whether different levels of peripheral blood (PB) and bone marrow (BM) infiltration may provide prognostic stratification in dogs with nMZL. The aims of the present prospective study were to assess the influence of PB and BM infiltration detected by flow cytometry (FC) on time to progression (TTP) and lymphoma-specific survival (LSS) in dogs with newly-diagnosed multicentric nMZL, and to establish a cut-off value of prognostic significance. Forty-five completely staged and treatment-naïf dogs with histologically-confirmed nMZL were enrolled. After staging, dogs received chemo-immunotherapy or chemotherapy. PB infiltration was significantly associated with TTP (p=0.001): dogs with PB infiltration <30% had a median TTP of 186 days, whereas dogs with PB infiltration ≥30% had a median TTP of 43 days. Additionally, vaccinated dogs had a significantly (p=0.012) longer TTP (399 days) compared with dogs receiving chemotherapy only (211 days). BM infiltration was significantly associated with LSS (p<0.001): dogs with BM infiltration <1% had a median LSS of 1403 days, those with BM infiltration 1-20% of 337 days, and those with BM infiltration ≥20% of 188 days. Normal LDH levels and the administration of chemo-immunotherapy also significantly improved LSS (560 vs 211 days, and 399 vs 211 days, respectively; p<0.001). PB and BM flow cytometric evaluation is an integral part of staging work-up in dogs with nMZL and has prognostic relevance.

Retrospective analysis of doxorubicin and prednisone as first-line therapy for canine B-cell lymphoma

BACKGROUND

A doxorubicin (DOX)-based chemotherapy protocol, CHOP, is the most effective treatment for canine high-grade B-cell lymphoma; however, the cost and time requirements associated with this protocol are not feasible for many pet owners. An alternative treatment option is the use of DOX, the most effective drug, in combination with prednisone. Prior studies with single-agent DOX included dogs with T-cell lymphoma, a known negative prognostic factor, which may have resulted in shorter reported survival times than if dogs with B-cell lymphoma were analyzed separately. The purpose of this study was to evaluate the outcome of dogs with high-grade B-cell lymphoma when treated with DOX and prednisone with or without L-asparaginase (L-ASP). Identification of prognostic factors was of secondary interest.

RESULTS

Thirty-three dogs were included in the study; 31 dogs were evaluable for response with an overall response rate of 84%. The median progression free survival (PFS) and overall survival (OS) were 147 days and 182 days, respectively. The one-year survival fraction was 23%. No variable other than protocol completion was found to be significant for either PFS or OS including historical prognostic factors such as substage, thrombocytopenia, and body weight.

CONCLUSIONS

Dogs with high-grade B-cell lymphoma treated with DOX and prednisone with or without L-ASP have similar response rates, PFS, and OS to prior studies that did not differentiate between lymphoma immunophenotype. This protocol is not a replacement for CHOP; however, it is an alternative if time and cost are factors, while providing therapeutic benefit greater than prednisone alone.

A retrospective study of flow cytometric characterization of suspected extranodal lymphomas in dogs

Flow cytometry (FC) is widely applied to characterize and stage nodal lymphomas in dogs because it has a short turnaround time, requires minimally invasive sampling, and allows contemporary evaluation of neoplastic cells in the primary lesion and of blood and marrow involvement. We investigated advantages and limitations of FC in suspected extranodal lymphomas in dogs. The likelihood of obtaining a suitable FC sample was significantly lower for aspirates of extranodal lesions than for lymph node aspirates. However, we noted no differences among different extranodal lesion sites. We also describe FC results for 39 samples compatible with extranodal lymphoma. A dominant population of large cells was easily identified on morphologic FC scattergrams in many cases. Phenotypic aberrancies were frequently present, mainly in T-cell lymphomas. Lymphoma cells were distinguishable from normal residual lymphocytes in >85% of cases, facilitating the quantification of putative blood and marrow involvement by FC. Despite the high percentage of non-diagnostic samples (32 of 73, >40%), we support the inclusion of FC in the diagnostic workup of suspected extranodal lymphomas in dogs, in conjunction with histopathology. Histopathology is the gold standard for diagnosing lymphoma, provides relevant information, including tissue invasion and epitheliotropism, but has a longer turnaround time.

A case of canine high-grade T-cell lymphoma immunophenotypically consistent with T-zone lymphoma

A 9-year-old spayed female Curly Coated Retriever was referred for evaluation of generalized peripheral lymphadenomegaly. The dog was clinically healthy on presentation with no anomalies detected on complete blood count, serum biochemistry, urinalysis, or three-view thoracic radiographs. Fine-needle aspiration (FNA) and cytology of the peripheral lymph nodes were consistent with lymphoma with an intermediate-sized lymphoid population. Flow cytometry of peripheral lymph nodes was consistent with a homogeneous population of CD4⁺ T cells that had lost expression of the pan-leukocyte antigen CD45. Variable expression of CD21, CD25, and class II major histocompatibility complex (MHC) were also noted. This was considered consistent with T-zone lymphoma (TZL), although the T cells were noted to be larger than usual based on flow cytometry. Due to the suspected indolent nature of this patient's disease and clinical progression, a careful monitoring approach was initially discussed with the owner. However, additional diagnostic testing was performed to confirm the diagnosis. Bone marrow cytology did not show any significant anomalies. The largest lymph node (left mandibular) was extirpated and submitted for histopathology. Based on the lymph node architecture, cellular features, and high mitotic activity, an unexpected diagnosis of peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) was made. The dog was started on CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy. This case illustrates the limitations of using flow cytometry as the sole means of diagnosing TZL and highlights the importance of using complementary tests when subtyping canine lymphoma, which is significant when considering a patient's treatment plan and prognosis.

Breed-associated risks for developing canine lymphoma differ among countries: an European canine lymphoma network study

BACKGROUND

Canine breeds may be considered good animal models for the study of genetic predisposition to cancer, as they represent genetic clusters. From epidemiologic and case collection studies it emerges that some breeds are more likely to develop lymphoma or specific subtypes of lymphoma but available data are variable and geographically inconsistent. This study was born in the context of the European Canine Lymphoma Network with the aim of investigating the breed prevalence of canine lymphoma in different European countries and of investigating possible breed risk of lymphoma overall and/or different lymphoma subtypes.

RESULTS

A total of 1529 canine nodal lymphoma cases and 55,529 control cases from 8 European countries/institutions were retrospectively collected. Odds ratios for lymphoma varied among different countries but Doberman, Rottweiler, boxer and Bernese mountain dogs showed a significant predisposition to lymphoma. In particular, boxers tended to develop T-cell lymphomas (either high- or low-grade) while Rottweilers had a high prevalence of B-cell lymphomas. Labradors were not predisposed to lymphoma overall but tended to develop mainly high-grade T-cell lymphomas. In contrast with previous studies outside of Europe, the European golden retriever population did not show any possible predisposition to lymphoma overall or to specific subtypes such as T-zone lymphoma.

CONCLUSION

Further prospective studies with more precise and consistent subtype identification are needed to confirm our retrospective results and to create the basis for the investigation of possible genes involved in different predispositions.

Flow Cytometric Characterization of S-phase Fraction and Ploidy in Lymph Node Aspirates from Dogs with Lymphoma

Canine lymphoma is a multifaceted disease encompassing numerous entities with different prognosis. Objective assessment of the proliferation rate is of importance from the pathological and clinical perspectives. Different methods have been described in the literature to assess proliferation rate, including evaluation of Ki67 expression in fresh lymph node (LN) aspirates measured by flow cytometry (FC). This test has a high accuracy in discriminating between low- and high-grade lymphomas, and provides prognostic information among high-grade B-cell lymphomas. DNA content analysis is less expensive and suitable for well-preserved samples. We describe DNA-content analysis using LN aspirates from 112 dogs with lymphoma. S-phase fraction (SPF) accurately discriminated between low- and high-grade lymphomas, with 3.15% being the best discriminating cut-off value. SPF values strongly correlated with Ki67 expression as assessed by FC. Survival analyses were restricted to 33 dogs with high-grade B-cell lymphoma receiving standardized multi-agent chemotherapy, but no significant result was obtained for SPF. We also describe a subset of aneuploid cases and their respective follow-up. We conclude that DNA content analysis may be combined with morphological examination of LN aspirates to improve the objectivity in lymphoma subtype classification in dogs. Further studies are needed to assess the possible prognostic role of SPF and ploidy status within specific lymphoma subtypes in dogs.

Loss of alpha-smooth muscle actin expression associated with chronic intestinal pseudo-obstruction in a young Miniature Bull Terrier

Background

Chronic intestinal pseudo-obstruction (CIPO) is a rare clinical syndrome in veterinary medicine characterized by severe intestinal dysmotility without evidence of mechanical occlusion of the intestinal lumen. The exact pathogenesis of CIPO is unknown.

Case presentation

A 1-year-old male Miniature Bull Terrier dog was presented with a history of chronic weight loss, regurgitation, lethargy, vomiting and diarrhea. The dog was submitted for exploratory laparotomy. A full thickness intestinal biopsy was taken and a CIPO was suspected. The clinical condition deteriorated and the dog was euthanized. At gross examination the small intestine was severely dilated. Histologically severe fibrosis of the submucosa and severe atrophy of the tunica muscularis were present in small intestine and colon. Immunohistochemical examination with a panel of antibodies for gastro-intestinal neuromuscular disease-associated antigens revealed a severely reduced expression of alpha-smooth muscle actin in the tunica muscularis.

Conclusions

This case report describes the gross, histological and immunohistochemical findings of CIPO affecting a 1-year-old Miniature Bull Terrier; on the basis of these findings a myopathic form of CIPO is hypothesized in this case.

Metabolic Abnormalities Detected in Phase II Evaluation of Doxycycline in Dogs with Multicentric B-Cell Lymphoma

Doxycycline has antiproliferative effects in human lymphoma cells and in murine xenografts. We hypothesized that doxycycline would decrease canine lymphoma cell viability and prospectively evaluated its clinical tolerability in client-owned dogs with spontaneous, nodal, multicentric, substage a, B-cell lymphoma, not previously treated with chemotherapy. Treatment duration ranged from 1 to 8 weeks (median and mean, 3 weeks). Dogs were treated with either 10 (n = 6) or 7.5 (n = 7) mg/kg by mouth twice daily. One dog had a stable disease for 6 weeks. No complete or partial tumor responses were observed. Five dogs developed grade 3 and/or 4 metabolic abnormalities suggestive of hepatopathy with elevations in bilirubin, ALT, ALP, and/or AST. To evaluate the absorption of oral doxycycline in our study population, serum concentrations in 10 treated dogs were determined using liquid chromatography tandem mass spectrometry. Serum levels were variable and ranged from 3.6 to 16.6 µg/ml (median, 7.6 µg/ml; mean, 8.8 µg/ml). To evaluate the effect of doxycycline on canine lymphoma cell viability in vitro, trypan blue exclusion assay was performed on canine B-cell lymphoma cell lines (17-71 and CLBL) and primary B-cell lymphoma cells from the nodal tissue of four dogs. A doxycycline concentration of 6 µg/ml decreased canine lymphoma cell viability by 80%, compared to matched, untreated, control cells (mixed model analysis, p < 0.0001; Wilcoxon signed rank test, p = 0.0313). Although the short-term administration of oral doxycycline is not associated with the remission of canine lymphoma, combination therapy may be worthwhile if future research determines that doxycycline can alter cell survival pathways in canine lymphoma cells. Due to the potential for metabolic abnormalities, close monitoring is recommended with the use of this drug in tumor-bearing dogs. Additional research is needed to assess the tolerability of chronic doxycycline therapy.

Prognostic significance of clinical presentation, induction and rescue treatment in 42 cases of canine centroblastic diffuse large B-cell multicentric lymphoma in the United Kingdom

Canine lymphoma is a heterogeneous group of diseases and many previous studies have evaluated the response of a mixed population of lymphoma cases to one specific treatment protocol. The aim of this retrospective study was to describe the outcome and prognostic factors in 42 cases of multicentric centroblastic diffuse large B-cell lymphoma treated with either a COP-type (35%) or CHOP-type (64%) induction chemotherapy. The objective response rate to induction therapy was 94%; entire dogs had a greater rate of complete vs partial remissions than neutered dogs (P = .017). Median progression-free survival for the first remission (PFS1) was 182 days; absence of anaemia at diagnosis (P = .002) and pretreatment neutrophil:lymphocyte ratio (NLR) below 9.44 (P = .015) were independently predictive of longer PFS1. Fifty-eight percent of dogs received rescue protocols with an objective response rate of 81%; 31% of dogs received further rescue protocols (up to a total of 5) and the median number of protocols administered were 2. Median overall survival (OS) was 322 days, the 1-year survival rate was 38% and the 2-year survival rate was 9%. Lymphocyte:monocyte ratio above 1.43 (P = .031), NLR below 11.44 (P = .009), the combination of induction and rescue therapy (P = .030) and the total number of doxorubicin doses used (P = .002) were independently predictive of longer OS. Use of a COP-type protocol induction compared with CHOP did not undermine OS providing doxorubicin was used as rescue therapy.

Canine nodal marginal zone lymphoma: Descriptive insight into the biological behaviour

Canine nodal marginal zone lymphoma (nMZL) is classified as an indolent lymphoma. Such lymphomas are typified by low mitotic rate and slow clinical progression. While the clinical behaviour of canine splenic MZL has been described, characterized by an indolent course and a good prognosis following splenectomy, there are no studies specifically describing nMZL. The aim of this study was to describe the clinical features of and outcome for canine nMZL. Dogs with histologically confirmed nMZL undergoing a complete staging work-up (including blood analysis, flow cytometry [FC] on lymph node [LN], peripheral blood and bone marrow, imaging, histology and immunohistochemistry on a surgically removed peripheral LN) were retrospectively enrolled. Treatment consisted of chemotherapy or chemo-immunotherapy. Endpoints were response rate (RR), time to progression (TTP) and lymphoma-specific survival (LSS). A total of 35 cases were enrolled. At diagnosis, all dogs showed generalized lymphadenopathy. One-third was systemically unwell. All dogs had stage V disease; one-third also had extranodal involvement. The LN population was mainly composed of medium-sized CD21+ cells with scant resident normal lymphocytes. Histology revealed diffuse LN involvement, referring to "late-stage" MZL. Median TTP and LSS were 149 and 259 days, respectively. Increased LDH activity and substage b were significantly associated with a shorter LSS. Dogs with nMZL may show generalized lymphadenopathy and an advanced disease stage. Overall, the outcome is poor, despite the "indolent" designation. The best treatment option still needs to be defined.

Specific immunotypes of canine T cell lymphoma are associated with different outcomes

Canine lymphoma is a heterogeneous disease with many different subtypes. Lymphoma of T cell type in particular is variable in outcome, and includes subtypes with non-progressive, slowly- and rapidly-progressive disease course. Association of immunotype with disease course is incompletely defined. Here, results of flow cytometric immunotyping of 127 canine T cell lymphomas were analyzed in relation to survival and progression free interval. Samples originated from 101 multicentric, 8 mediastinal, 6 cutaneous, 5 hepatosplenic, 5 gastrointestinal and 2 other anatomic subtypes of T cell lymphoma. Compared to multicentric T cell lymphoma, gastrointestinal lymphoma had shorter survival and progression free interval, and hepatosplenic lymphoma had shorter survival. Among dogs with multicentric T cell lymphoma, immunotypes of CD4⁺/CD8^-/MHCII⁺, CD4^-/CD8⁺/MHCII⁺ and CD4^-/CD8⁺/MHCII^- were associated with longer survival times than the immunotype of CD4⁺/CD8^-/MHCII^-, and immunotypes of CD4⁺/CD8^-/MHCII⁺, CD4^-/CD8⁺/MHCII^-, and CD4^-/CD8^-/MHCII⁺ were associated with longer progression free intervals. Dogs with multicentric T cell lymphoma and concurrent leukemia had shorter survival but similar progression free interval compared to those without leukemia. Body weight, sex, hypercalcemia, cell size, expression of CD3 and use of combination or single agent chemotherapy did not significantly affect outcome of multicentric TCL.

Cytodiagnostics of canine lymphomas - possibilities and limitations

Malignant lymphomas are one of the most common malignant tumours occurring in dogs. The basic method of lymphoma diagnosis in human, as well as in canine oncology is histopathology supported by immunohistochemistry. It was suggested that in veterinary medicine excisional biopsy of lymph node and histopathology should be considered only where the cytologic diagnosis is equivocal or needs to be confirmed. There are at least three basic reasons for which cytological examination ought to be accepted as a sufficient and reliable diagnostic method for lymphoma in dogs. Firstly, most dog owners consider the fine-needle biopsy as an acceptable non-harmful method of sample collection. Secondly, an increasing number of studies recommend cytology as an accurate test for diagnosing and subtyping canine lymphoma. Finally, the vast majority of canine lymphoma subtypes belong to 4-5 categories characterized by a typical cytological picture. Immunocytochemical staining of cytological smears gives new diagnostic possibilities, such as detection of markers better characterizing given growth or a potential goal for target therapy in individual cases (for example inhibitors of platelet-derived growth factor).

Canine Lymphoma, More Than a Morphological Diagnosis: What We Have Learned about Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common canine aggressive B-cell lymphoma worldwide, and new recent molecular approaches have shown that DLBCL constitutes a heterogeneous tumor that cannot be unraveled by morphology and immunophenotype. DLBCL behaves aggressively, typically progressing over a short period of time, and the therapy response may be difficult to be predicted. Recently, the rate of bone marrow infiltration by flow cytometry has been demonstrated to be prognostic, but more sensible markers are needed. As the clinical behavior is different, there is vast clinical and basic research devoted to identifying prognostically or biologically distinct DLBCL subgroups. Transcriptomic analysis by gene expression profile, copy number variations by array comparative genomic hybridization and epigenetic perturbations have tentatively described this heterogeneity. Molecular subgroups using oncogenic pathways and target genes have also been correlated to different outcome in a small number of cases. The objectives of this review are to summarize the current knowledge on the biology, clinical, and pathological characteristics of canine DLBCL. To date, DLBCL probably is the most investigated tumor in veterinary medicine, and its relevance as spontaneous model for human DLBCL has been confirmed by these studies. In future, these discoveries will ultimately lead to a better understanding of the underlying disease mechanisms, possibly translating into more effective therapeutic strategies.

BCL2 and MYC are expressed at high levels in canine diffuse large B-cell lymphoma but are not predictive for outcome in dogs treated with CHOP chemotherapy

Diffuse large B-cell lymphoma (DLBCL) is the most common haematopoietic malignancy in dogs. Recently, MYC and BCL2 expression levels determined with immunohistochemistry (IHC) were found to be prognostic in people with DLBCL. We hypothesized that canine DLBCL can be similarly subdivided into prognostic subtypes based on expression of MYC and BCL2. Cases of canine DLBCL treated with CHOP chemotherapy were retrospectively collected and 43 dogs had available histologic tissue and complete clinical follow-up. Median values of percent immunoreactive versus immunonegative cells were used to determine positive or negative expression status. Completion of CHOP was significantly associated with a positive outcome. Compared with human patients, our canine DLBCL patients had high IHC expression of both MYC and BCL2, and relative expression levels of one or both markers were not associated with clinical outcome.

Chronic lymphocytic leukemia transformation into high-grade lymphoma: a description of Richter's syndrome in eight dogs

Richter's syndrome (RS) is the development of an aggressive lymphoma in patients with chronic lymphocytic leukaemia (CLL). In humans, RS occurs in 2-20% of CLL, which transform into diffuse large B-cell lymphoma but reports in dogs are scarce. This study retrospectively describes eight dogs with CLL progressing into RS. A database including 153 dogs with CLL (93T CD8+ and 55 B-CLL) was interrogated and RS was demonstrated in eight cases (representing 5.2% of total CLL): two with T-cell (2.2% of T CLL) and six with a B-cell immunophenotype (10.9% of B-CLL). When RS occurred, lymphocytes were decreased compared to CLL. Five dogs had anaemia and two dogs thrombocytopenia. Frequent clinical signs included lymph node swelling, coughing, vomiting, neurological signs and weight loss. Independently from the therapy, RS was associated with a short survival (median 41 days). RS should be considered as an unfavourable evolution in canine CLL.

Array-based comparative genomic hybridization analysis reveals chromosomal copy number aberrations associated with clinical outcome in canine diffuse large B-cell lymphoma

Canine Diffuse Large B-cell Lymphoma (cDLBCL) is an aggressive cancer with variable clinical response. Despite recent attempts by gene expression profiling to identify the dog as a potential animal model for human DLBCL, this tumor remains biologically heterogeneous with no prognostic biomarkers to predict prognosis. The aim of this work was to identify copy number aberrations (CNAs) by high-resolution array comparative genomic hybridization (aCGH) in 12 dogs with newly diagnosed DLBCL. In a subset of these dogs, the genetic profiles at the end of therapy and at relapse were also assessed. In primary DLBCLs, 90 different genomic imbalances were counted, consisting of 46 gains and 44 losses. Two gains in chr13 were significantly correlated with clinical stage. In addition, specific regions of gains and losses were significantly associated to duration of remission. In primary DLBCLs, individual variability was found, however 14 recurrent CNAs (>30%) were identified. Losses involving IGK, IGL and IGH were always found, and gains along the length of chr13 and chr31 were often observed (>41%). In these segments, MYC, LDHB, HSF1, KIT and PDGFRα are annotated. At the end of therapy, dogs in remission showed four new CNAs, whereas three new CNAs were observed in dogs at relapse compared with the previous profiles. One ex novo CNA, involving TCR, was present in dogs in remission after therapy, possibly induced by the autologous vaccine. Overall, aCGH identified small CNAs associated with outcome, which, along with future expression studies, may reveal target genes relevant to cDLBCL.

Platelet-derived growth factors and receptors in Canine Lymphoma

Platelet-derived growth factors (PDGFs) belong to a family of polypeptide growth factors that signal through cell surface tyrosine kinase receptors to stimulate growth, proliferation and differentiation. Platelet-derived growth factor receptors (PDGFRs) are also considered important targets for specific kinase inhibitors in the treatment of several human tumours. The aim of this study was to investigate the role of PDGF-A, PDGF-B, PDGFR-α and PDGFR-β in canine lymphoma by determining gene and protein expression in lymph nodes of dogs with diffuse large B-cell lymphoma (DLBCL), peripheral T-cell lymphoma (PTCL), T-lymphoblastic lymphoma (T-LBL) and in healthy control dogs. One lymph node was also studied at the end of therapy in a subset of dogs in remission for DLBCL. In controls, PDGF-A, PDGFR-α and PDGFR-β mRNA levels were significantly higher than in DLBCLs, PTCLs and T-LBLs. However, PDGFR-α and PDGFR-β were minimally expressed by lymphocytes and plasma cells in normal lymph nodes as determined by immunohistochemistry, while neoplastic B and T cells showed the highest score (P <0.05). This discordant result may be compatible with the constitutive expression of these molecules by endothelial cells and fibroblasts in normal lymph nodes, thereby influencing gene expression results. Furthermore, these cells were not included in the immunohistochemical analysis. Similarly, dogs with DLBCL that were in remission at the end of therapy showed significantly higher gene expression of PDGFs and receptors than at the time of diagnosis and with an opposite trend to the protein assay. PDGF-B protein and mRNA were overexpressed in PTCLs and T-LBLs when compared with DLBCLs and controls (P <0.05). Additionally, there was a correlation between protein expression of PDGF-B and both PDGFRs in PTCLs and T-LBLs, suggesting an autocrine or paracrine loop in the aetiology of aggressive canine T-cell lymphomas. These data provide a rationale for the use of PDGFR antagonists in the therapy of aggressive T-cell lymphomas, but not in DLBCLs.

Dissecting the regulatory microenvironment of a large animal model of non-Hodgkin lymphoma: evidence of a negative prognostic impact of FOXP3+ T cells in canine B cell lymphoma

The cancer microenvironment plays a pivotal role in oncogenesis, containing a number of regulatory cells that attenuate the anti-neoplastic immune response. While the negative prognostic impact of regulatory T cells (Tregs) in the context of most solid tissue tumors is well established, their role in lymphoid malignancies remains unclear. T cells expressing FOXP3 and Helios were documented in the fine needle aspirates of affected lymph nodes of dogs with spontaneous multicentric B cell lymphoma (BCL), proposed to be a model for human non-Hodgkin lymphoma. Multivariable analysis revealed that the frequency of lymph node FOXP3⁺ T cells was an independent negative prognostic factor, impacting both progression-free survival (hazard ratio 1.10; p = 0.01) and overall survival (hazard ratio 1.61; p = 0.01) when comparing dogs showing higher than the median FOXP3 expression with those showing the median value of FOXP3 expression or less. Taken together, these data suggest the existence of a population of Tregs operational in canine multicentric BCL that resembles thymic Tregs, which we speculate are co-opted by the tumor from the periphery. We suggest that canine multicentric BCL represents a robust large animal model of human diffuse large BCL, showing clinical, cytological and immunophenotypic similarities with the disease in man, allowing comparative studies of immunoregulatory mechanisms.

Canine T-zone lymphoma: unique immunophenotypic features, outcome, and population characteristics

Background

Canine T‐cell lymphoma (TCL) is clinically and histologically heterogeneous with some forms, such as T‐zone lymphoma (TZL), having an indolent course. Immunophenotyping is an important tool in the classification of TCL in people, and can be equally useful in dogs.

Hypothesis/Objectives

We hypothesized that loss of expression of the CD45 antigen is a specific diagnostic feature of TZL.

Animals

Twenty dogs with concurrent histology and immunophenotyping by flow cytometry were studied in depth. An additional 494 dogs diagnosed by immunophenotyping were used to characterize the population of dogs with this disease.

Methods

Lymph node biopsies from 35 dogs with TCL were classified by 2 pathologists using WHO criteria. Twenty lymph nodes were from dogs with CD45− TCL and 15 were from CD45+ TCL. The pathologists were blinded to the flow cytometry findings. Outcome information was sought for the 20 dogs with CD45− lymphoma, and population characteristics of the additional 494 dogs were described.

Results

All 20 CD45− cases were classified as TZL. The 15 CD45+ cases were classified as aggressive TCL and are described in an accompanying paper. TZL cases had a median survival of 637 days. Examination of 494 additional dogs diagnosed with TZL by immunophenotyping demonstrated that 40% of cases are in Golden Retrievers, are diagnosed at a median age of 10 years, and the majority have lymphadenopathy and lymphocytosis.

Conclusions

TZL has unique immunophenotypic features that can be used for diagnosis.

Flow cytometric characterization and clinical outcome of CD4+ T-cell lymphoma in dogs: 67 cases

Background

Canine T‐cell lymphoma (TCL) is conventionally considered an aggressive disease, but some forms are histologically and clinically indolent. CD4 TCL is reported to be the most common subtype of TCL. We assessed flow cytometric characteristics, histologic features when available, and clinical outcomes of CD4+ TCL to determine if flow cytometry can be used to subclassify this group of lymphomas.

Objective

To test the hypothesis that canine CD4+ T‐cell lymphoma (TCL) is a homogeneous group of lymphomas with an aggressive clinical course.

Animals

Sixty‐seven dogs diagnosed with CD4+ TCL by flow cytometry and treated at 1 of 3 oncology referral clinics.

Methods

Retrospective multivariable analysis of outcome in canine CD4+ TCL including patient characteristics, treatment, and flow cytometric features.

Results

The majority of CD4+ TCL were CD45+, expressed low class II MHC, and exhibited an aggressive clinical course independent of treatment regimen (median survival, 159 days). Histologically, CD4+ TCL were classified as lymphoblastic or peripheral T cell. Size of the neoplastic lymphocytes had a modest effect on both PFI and survival in this group. A small number of CD4+ TCL were CD45− and class II MHC high, and exhibited an apparently more indolent clinical course (median survival not yet reached).

Conclusions and Clinical Importance

Although the majority of CD4+ TCL in dogs had uniform clinical and flow cytometric features and an aggressive clinical course, a subset had a unique immunophenotype that predicts significantly longer survival. This finding strengthens the utility of flow cytometry to aid in the stratification of canine lymphoma.