Breed Distribution and Clinical Characteristics of B Cell Chronic Lymphocytic Leukemia in Dogs

Canine polyostotic B-cell lymphoma: a case with clinical, immunohistochemical, and flow cytometric characterization, and review of the literature

An 8-mo-old Mastiff-cross dog with bone pain and lytic-proliferative lesions in the radius, ulna, femur, vertebral spinous processes, and ribs, was diagnosed with lymphoma. The dog also had anemia and thrombocytopenia, and atypical circulating lymphocytes were identified as B cells by flow cytometry. Due to the multicentric, rapidly progressive disease, the dog was euthanized. Postmortem examination confirmed extensive bone replacement by lymphoma, and infiltration of lymph nodes, spleen, and liver. Histomorphology and immunohistochemistry showed a diffuse large B-cell lymphoma that was immunopositive for PAX5 and CD20, and immunonegative for CD3. Lymphoma of bone is rare in dogs and humans, and is most frequently reported in pediatric individuals. Including our case, 7 of 14 reported cases occurred in dogs <2-y-old, and all but 1 had polyostotic disease. Long bones, ribs, and vertebrae were affected most often, and the distal metaphyseal region was targeted in long bones. Visceral and nodal tissue infiltration was common, and all tumors had a diffuse architecture. Most dogs with polyostotic lymphoma were euthanized at the time of diagnosis, and survival was <6 wk in dogs that were treated with chemotherapy or surgery.

Flow cytometric-based detection of CD80 is a useful diagnostic marker of acute myeloid leukemia in dogs

Introduction

CD80, a co-stimulatory molecule required for optimal T cell activation, is expressed on antigen-presenting cells, including monocytes and dendritic cells, in dogs and humans. We hypothesized that CD80 would be expressed on tumor cells in dogs from acute myeloid leukemia (AML) but not dogs with lymphoid neoplasms.

Methods and results

We first evaluated the cellular staining pattern of a hamster anti-murine CD80 antibody (clone 16-10A1, ThermoFisher Scientific Cat# 17-0801-82, RRID: AB_469417) in blood and bone marrow aspirates from healthy dogs. Using flow cytometric analysis and examination of modified Wright's-stained cytologic smears of unsorted and flow cytometric or immunomagnetic bead-sorted leukocytes, we show that the antibody binds to mature and immature neutrophils and monocytes, but not lymphocytes or eosinophils, in blood and bone marrow. We then added the antibody to routine flow cytometric panels for immunophenotyping hematopoietic neoplasms in dogs. We found that the antibody labeled tumor cells in 72% of 39 dogs with AML and 36% of 11 dogs with acute leukemia expressing lymphoid and myeloid markers ("mixed lineage") but none of the dogs with B (n = 37) or T (n = 35) lymphoid neoplasms. A higher proportion of tumor cells in dogs with AML were labeled with the anti-CD80 antibody vs antibodies against other myeloid-associated antigens, including CD4 (36%, p = 0.003), CD11b (44%), CD11c (46%), CD14 (38%, p = 0.006) and CD18 (59%, clone YFC118). In contrast, antibodies against CD11b and CD11c bound to tumor cells in 8-32% of the lymphoid neoplasms.

Discussion

We show that CD80, as detected by antibody clone 16-10A1, is a sensitive and specific marker for AML and would be useful to include in flow cytometric immunophenotyping panels in dogs.

Flow Cytometric Features of B- and T-Lmphocytes in Reactive Lymph Nodes Compared to Their Neoplastic Counterparts in Dogs

An in-depth knowledge of non-neoplastic patterns is fundamental to diagnose neoplasia. In the present study, we described the flow cytometric (FC) cell size (FSC) and fluorescence intensity (MFI) of B- and T-lymphocytes in 42 canine reactive lymph nodes and 36 lymphomas. Proliferative activity (Ki67%) in reactive lymph nodes was also reported. Reactive lymph nodes were composed of a mixed population of small and large T (CD5+) and B (CD21+) cells. Small T-cells were larger in size than small B-cells, and large T-cells were larger than large B-cells. Small T-cells were composed of CD5+CD21- and CD5+CD21+dim subpopulations. Large B-cells were <20% in reactive lymph nodes and >20% in lymphomas and showed a higher FSC in lymphomas than in reactive lymph nodes. Large T-cells were <4% in reactive lymph nodes and >4% in lymphomas and showed a higher CD5 MFI in lymphomas (if expressed) compared to reactive lymph nodes. A subset of CD5+CD21+dim lymphocytes was recognized in addition to CD5+CD21- and CD5-CD21+ cells. In T-zone lymphomas, neoplastic cells had higher FSC and CD21 MFI values than small CD5+CD21+dim cells in reactive lymph nodes. Ki67% values were higher than those reported in normal lymph nodes, and largely overlapped with those reported in low-grade lymphomas and partially in high-grade lymphomas. Our results may contribute to making a less operator-dependent FC differential between lymphoma and reactive lymph nodes.

A series of heterogeneous lymphoproliferative diseases with CD3 and MUM1 co-expressed in cats and dogs

Lymphoma diagnosis in dogs and cats is continually evolving as new subtypes and human correlates are being recognized. In humans, T-cell lymphomas with MUM1 expressed and plasma cell neoplasia or B-cell lymphomas with CD3 expressed aberrantly are reported only rarely. We report here a case series of tumors in dogs and cats with CD3 and MUM1 co-expressed as determined by immunocytochemistry or immunohistochemistry. Lineage was assigned for these tumors by 3 board-certified pathologists and a veterinary immunologist based on review of clinical and cellular features and the results of ancillary testing including PCR for antigen receptor rearrangements, flow cytometry, and serum protein electrophoresis with immunofixation. In cats, 7 of 7 tumors, and in dogs, 3 of 6 tumors with CD3 and MUM1 co-expressed had clonal rearrangement of the immunoglobulin gene or serum monoclonal immunoglobulin, consistent with a diagnosis of a plasma cell neoplasia or myeloma-related disorder with CD3 expressed aberrantly. Disease was often disseminated; notably, 3 of 7 feline cases had cutaneous and/or subcutaneous involvement in the tarsal area. In dogs, 3 of 6 cases had a clonal T-cell receptor gamma result and no clonal immunoglobulin gene rearrangement and were diagnosed as a T-cell tumor with MUM1 expressed. The use of multiple testing modalities in our series of tumors with plasma-cell and T-cell antigens in dogs and cats aided in the comprehensive identification of the lymphoproliferative disease subtype.

The use of flow cytometry for diagnosis and immunophenotyping in chronic lymphocytic leukemia in a dog: Clinical case report

BACKGROUND

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in dogs. It is characterized by the proliferation of neoplastic lymphocytes in the bone marrow, which are morphologically normal (mature), but non-functional. CLL in canines commonly originates in cytotoxic T lymphocytes (TCD8+), and although there is controversy regarding the prognostic value of the immunophenotype, this cell lineage may be associated with a good prognosis.

CASE DESCRIPTION

A 10-year-old, entire female, mixed-breed dog was brought to the University Hospital of the Veterinary Faculty (UdelaR) for consultation because a routine pre-surgical check-up revealed lymphocytic leukocytosis, normocytic anemia, and hyperglobulinemia due to an oligoclonal gammopathy. The ultrasound revealed splenomegaly. PCR performed on blood was negative for Ehrlichia canis. Blood and bone marrow flow cytometry was performed to complement the diagnosis and carry out the immunophenotype, which showed CLL of CD8+ T-cell lineage. The clinical suspicion of CLL was confirmed by a myelogram. Chemotherapy treatment based on alkylating agents and glucocorticoids was established. So far, the patient has an overall survival of 13 months with a good response to treatment.

CONCLUSION

The combination of the immunophenotyping test, the myelogram, and the hematological and biochemical profile confirmed the presence of T-CLL in our patient. Flow cytometry, increasingly used in veterinary medicine, allowed us to confirm the diagnosis of CLL originating in cytotoxic T lymphocytes in our patient, through the presence of positive staining of primary antibodies specific for the canine species CD45, CD3, CD5, and CD8 and the absence of staining for CD4, CD21, and CD34.

Hyphema and secondary glaucoma as a presenting complaint in a dog with chronic lymphocytic leukemia

A 5-year-old Pomeranian was diagnosed with anterior uveitis, hyphema, and secondary glaucoma OD. Concurrent retinal hemorrhage, perivascular sheathing, and papilledema were identified OS. Work-up identified small cell lymphocytosis (>900 × 109/L), anemia, and thrombocytopenia. The patient was diagnosed with B-cell chronic lymphocytic leukemia as a cause of the ocular findings.

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.

The impact of peripheral blood cell ratios in dogs with diffuse B-cell small lymphocytic lymphoma treated with CHOP protocol

In this study, pre-chemotherapy hematological values of 14 dogs diagnosed with diffuse B-cell small lymphocytic lymphoma were compared with the hematological data of 26 healthy dogs. Neutrophil/lymphocyte ratio (NLR), lymphocyte/monocyte ratio (LMR), platelet/lymphocyte ratio (PLR) and platelet/neutrophil ratio (PNR) were evaluated between two groups. Anemia and an increased total leukocyte count were observed in dogs with lymphoma compared to healthy ones. The PNR value was found to be significantly lower in dogs with lymphoma, It was concluded that more comprehensive studies studies are needed to clearly understand the diagnostic and prognostic importance of hematological parameters in B-cell small lymphocytic lymphoma of dogs.

Detection and Characterization of Paraproteinemia in Canine Chronic B-cell Lymphocytic Leukemia Using Routine and Free Light Chain Immunofixation

BACKGROUND

Hyperglobulinemia is reported in 26% of canine chronic B-cell lymphocytic leukemia (B-CLL) cases. However, few cases have been characterized by protein electrophoresis and immunofixation (IF), and the incidence of a monoclonal protein (M-protein) is unknown using these techniques.

OBJECTIVE

To characterize and determine the proportion of canine B-CLL cases with an M-protein using plasma protein electrophoresis (PPE), routine and free light chain (fLC) IF, and to assess if productive B-CLL cases express MUM1/IRF4 by cell tube block (CTB).

METHODS

PPE, routine (targeting IgG, IgA, IgM, IgG4, and light chain) and fLC IF were performed using 48 dog B-CLL plasma samples from patients diagnosed via peripheral blood flow cytometry. CTB was performed on a separate cohort of 15 patients.

RESULTS

Hyperproteinemia (>7.5 g/dL) was present in 17/48 cases (35%). An M-protein was detected in 32/48 cases (67%). Of these, 19/32 cases (59%) had only complete (monoclonal heavy and light chain) M-proteins detected, 10/32 cases (31%) had both complete and fLC M-proteins detected, and 3/32 cases (9%) had only an fLC M-protein detected. IgM was the most common clonal immunoglobulin isotype detected (23 cases). CD21⁺ cell counts were higher in cases with detectable M-protein. Plasma fLC IF suggested β-γ region interference, likely caused by clotting proteins. All B-CLL cases consistently expressed PAX5 and did not express MUM1/IRF4.

CONCLUSIONS

Most B-CLL cases had an M-protein and were not hyperproteinemic. Most cases with paraproteins had a complete IgM monoclonal gammopathy; a subset had documented fLCs. The prognostic significance of heavy and fLC presence should be evaluated.

A bitesize introduction to canine hematologic malignancies

Hematologic malignancies are frequently diagnosed in dogs and result in a spectrum of clinical signs associated with specific disease types. The most frequently encountered hematologic tumors in dogs include lymphoma, lymphoid and myeloid leukemias, and mast cell, plasma cell, and histiocytic neoplasias. Coupled with the heterogeneous presentations of the different categories and subtypes of canine hematologic malignancies, outcomes for these tumors are also variable. Considering this, appropriate treatment options range from active surveillance to curative intent approaches harnessing surgical, chemotherapeutic, and radiation-based modalities. The underlying pathology of many of these diseases bears remarkable resemblance to that of the corresponding diagnosis made in human patients. We introduce some of the pathogenic drivers of canine hematologic cancers alongside their clinical presentations. An overview of standard-of-care therapies for each of these diseases is also provided. As comparative oncology gains recognition as a valuable setting in which to investigate the pathogenesis of neoplasia and provide powerful, clinically relevant, immunocompetent models for the evaluation of novel therapies, the number of clinicians and scientists participating in cancer research involving dogs is expected to increase. This review aims at providing an introductory overview of canine hematologic malignancies.

Case Report: Long-Term Survival of a Dog With Chronic Lymphocytic Leukemia Treated With Chlorambucil, Prednisolone, and Imatinib

A 7-year-old castrated male Poodle dog presented with chronic progressive lymphocytosis. Hematologic and peripheral blood smear findings included remarkable lymphocytosis with well-differentiated small lymphocytes. Cytology of bone marrow aspirate showed hypercellular integrity with infiltration of small mature lymphocytes, accounting for 45% of all nucleated cells. Flow cytometry of blood and marrow samples revealed neoplastic lymphocytes predominantly expressing the CD21 molecule. B-cell chronic lymphocytic leukemia (CLL) was diagnosed on an immunophenotypic analysis. Administrations of prednisolone and chlorambucil were initiated and the response was unremarkable. Therefore, additional treatment with imatinib was provided, which resolved the hematologic abnormalities associated with CLL. Flow cytometry after ~1 year of treatment showed normalization of the count of lymphocytes positive for CD21 and resolved hematologic lymphocytosis. The dog was followed-up for 2 years, and there were no severe adverse effects. This case indicates that imatinib may be a good option as an adjunctive therapy with prednisolone and chlorambucil treatment for CLL in dogs without treatment response.

An aggressive CD4- CD8- T-cell neoplasm in young English bulldogs

T-cell leukemia/lymphoma accounts for roughly 30% of all types of lymphoproliferative neoplasia in dogs. Two forms of T-cell lymphoma (T-zone and peripheral T-cell lymphoma) exhibit breed-specific predilections. During the course of routine immunophenotyping, we observed a breed-specific presentation of a unique form of T-cell leukaemia in young English bulldogs. To describe the clinical presentation and outcome of a novel T-cell leukaemia in English bulldogs and determine the frequency of this neoplasm in other breeds. The Clinical Hematopathology database, containing immunophenotyping data from peripheral blood of nearly 11 900 dogs, was queried for the phenotype observed in young English bulldogs: CD45⁺ CD4^- CD8^- CD5⁺ CD3⁺ class II major histocompatibility complex (MHC)-low T-cell leukaemia. Clinical presentation, treatment, and survival data were collected for a subset of cases. Fifty-five English bulldog cases and 64 cases of other breeds were identified. No other breed was represented by >5 cases. Complete medical records were obtained for 50 bulldogs. Median age at diagnosis was 3 years and 76% of cases were male. Median lymphocyte count was 44 286 lymphocytes/μl (range, 1800-317 684/μl) and lymphocytes were described as small to intermediate-sized. Many dogs were thrombocytopenic and had liver and spleen involvement, but not lymphadenopathy. Bulldogs that received multi-agent chemotherapy had longer median survival times (83 days) compared to dogs that received no treatment (6 days) or less aggressive therapy (15 days) (p = .001). Non-bulldogs had similar outcomes. CD4^- CD8^- class II MHC-low T-cell leukaemia has an aggressive clinical course and predilection for young English bulldogs. Breed-specific presentation suggests an underlying genetic cause.

Clinical outcome and prognostic factors in dogs with B-cell chronic lymphocytic leukemia: A retrospective study

BACKGROUND

B-cell chronic lymphocytic leukemia (BCLL) in dogs generally is considered an indolent disease, but previous studies indicate a wide range in survival times.

OBJECTIVES

We hypothesized that BCLL has a heterogeneous clinical course, similar to chronic lymphocytic leukemia in humans. We aimed to assess presentation and outcome in dogs with BCLL and evaluate the prognostic relevance of clinical and flow cytometric factors.

ANIMALS

One hundred and twenty-one dogs with BCLL diagnosed by flow cytometry. Three breed groups were represented: small breed dogs (n = 55) because of increased risk of BCLL; Boxers (n = 33) because of preferential use of unmutated immunoglobulin genes; and other breeds (n = 33).

METHODS

Retrospective study reviewing signalment, clinicopathologic data, physical examination findings, treatment, and survival of dogs with BCLL. Cellular proliferation, determined by the percentage of Ki67-expressing CD21+ B-cells by flow cytometry, was measured in 39 of 121 cases. Clinical and laboratory variables were evaluated for association with survival.

RESULTS

The median survival time (MST) for all cases was 300 days (range, 1-1644 days). Boxers had significantly shorter survival (MST, 178 days) than non-Boxers (MST, 423 days; P < .0001), and no significant survival difference was found between small breeds and other non-Boxer breeds. Cases with high Ki67 (>40% Ki67-expressing B-cells) had significantly shorter survival (MST, 173 days) than did cases with <40% Ki67 (MST undetermined; P = .03), regardless of breed. Cases with a high lymphocyte count (>60 000 lymphocytes/μL) or clinical signs at presentation had significantly shorter survival.

CONCLUSIONS AND CLINICAL IMPORTANCE

B-cell chronic lymphocytic leukemia had a variable clinical course and Boxer dogs and cases with high Ki67 had more aggressive disease.

Progressive gammopathy and coagulopathy in a young English bulldog

A restricted polyclonal or biclonal gammopathy resulting in bleeding tendencies was diagnosed in a young, neutered male English bulldog with concurrent splenomegaly, anemia, and severe elevations in IgM and, to a lesser degree, IgA immunoglobulins. There was a positive clinical response to treatment with prednisone and chlorambucil. This case bears similarity to a recently published syndrome of polyclonal gammopathy that is not neoplastic in origin in this breed. Key clinical message: The current case describes the management and clinical course of a recently described syndrome of polyclonal gammopathy in English bulldogs.

Diffuse Small B-Cell Lymphoma: A High-Grade Malignancy

The most common subtype of lymphoma in the dog is diffuse large B-cell lymphoma (DLBCL). The remaining forms of B-cell lymphoma in dogs are categorized as small-to-intermediate in size and include marginal zone, follicular, mantle cell, and small-cell lymphocytic lymphoma. Marginal zone lymphoma and follicular lymphoma have readily identifiable unique histologic features while other forms of small B-cell lymphoma in the dog are poorly described by histopathology. Forty-seven cases of nodal small B-cell lymphoma identified by flow cytometry (small cell size based on forward scatter) with concurrent histopathology were reviewed. These cases fell into 3 histologic subtypes: marginal zone lymphoma, follicular lymphoma, and a diffuse form of small B-cell lymphoma with consistent features. As a descriptive term, we refer to the latter subtype as diffuse small B-cell lymphoma (DSBCL) until it can be further characterized by gene expression profiling and other molecular tools. Clinical presentation of DSBCL was compared to cases of histologically confirmed DLBCL and clinical follow-up was obtained for 22 of the 27 cases of DSBCL. This subset of diffuse small B-cell lymphoma had an overall median survival of 140 days. The expression of CD21, class II MHC and CD25 by flow cytometry did not differ between DSBCL and the other histologic subtypes of small cell B-cell lymphoma making histopathology the only current method of classification.

Polyclonal B-cell lymphocytosis in English bulldogs

Background

English bulldogs disproportionally develop an expansion of small B‐cells, which has been interpreted as B‐cell chronic lymphocytic leukemia (BCLL). However, clonality testing in these cases has often not been supportive of neoplasia.

Hypothesis

English bulldogs have a syndrome of nonneoplastic B‐cell expansion.

Animals

Eighty‐four English bulldogs with small‐sized CD21+ B‐cell lymphocytosis in the blood as determined by flow cytometry.

Methods

This is a retrospective study. We characterized this syndrome by assessing B‐cell clonality, clinical presentation, flow cytometric features, and immunoglobulin gammopathy patterns. We identified 84 cases with CD21+ lymphocytosis among 195 English bulldogs with blood samples submitted to the Colorado State University‐Clinical Immunology laboratory for immunophenotyping between 2010 and 2019. Flow cytometry features were compared to normal B‐cells and BCLL cases. PCR for antigen receptor rearrangements (PARR) by multiple immunoglobulin primers was performed to assess B‐cell clonality. A subset of cases with gammopathy were examined by protein electrophoresis, immunofixation, and immunoglobulin subclass ELISA quantification.

Results

Seventy percent (58/83) of cases had polyclonal or restricted polyclonal immunoglobulin gene rearrangements, suggesting nonmalignant B‐cell expansion. The median age of all dogs in the study was 6.8 years and 74% were male. The median (range) lymphocyte count was 22 400/μL (2000‐384 400/μL) and B‐cells had low expression of class II MHC and CD25. Splenomegaly or splenic masses were detected in 57% (26/46) of cases and lymphadenopathy in 11% (7/61). Seventy‐one percent (52/73) of cases had hyperglobulinemia and 77% (23/30) with globulin characterization had IgA ± IgM polyclonal or restricted polyclonal gammopathy patterns.

Conclusions and Clinical Importance

Polyclonal B‐cell lymphocytosis in English bulldogs is characterized by low B‐cell class II MHC and CD25 expression, splenomegaly and hyperglobulinemia consisting of increased IgA ± IgM. We hypothesize that this syndrome has a genetic basis.

Rapid clinical progression of B-cell chronic lymphocytic leukemia in a horse

CASE DESCRIPTION

A 17-year-old Friesian gelding was examined at a referral hospital because of a 1-month history of mild exercise intolerance and marked lymphocytosis.

CLINICAL FINDINGS

Physical examination revealed no peripheral lymphadenopathy or other abnormalities. Results of an abdominal palpation examination per rectum and thoracic and abdominal ultrasonographic examinations were unremarkable. B-cell chronic lymphocytic leukemia (CLL) was diagnosed on the basis of severe lymphocytosis and positive expression of the B-cell marker CD20 by lymphocytes in the bone marrow and peripheral blood.

TREATMENT AND OUTCOME

Treatment with prednisolone (2 mg/kg [0.9 mg/lb], PO, every other day) and chlorambucil (20 mg/m², PO, every 3 weeks for 2 doses, then every 2 weeks) was initially associated with improvement in clinical signs and a decrease in the lymphocyte count. However, 3 weeks after administration of the first dose of chlorambucil, the lymphocyte count began to increase. One week later, the horse developed episodes of recurrent fever and the lymphocyte count continued to increase. Despite continued administration of the prednisolone-chlorambucil protocol, the horse's clinical condition deteriorated rapidly, and it was euthanized 6 weeks after initial examination at the referral hospital because of a poor prognosis. A necropsy was not performed.

CLINICAL RELEVANCE

B-cell CLL has been infrequently described in horses. This report was the first to describe the use of chemotherapy, albeit unsuccessful, for the treatment of B-cell CLL in a horse. This information should be useful for guiding expectations for prognosis and management of other horses affected with the disease.

Multicenter flow cytometry proficiency testing of canine blood and lymph node samples

BACKGROUND

Flow cytometry (FC) is used increasingly in veterinary medicine for further characterization of hematolymphoid cells. Guidelines for optimizing assay performance and interpretation of results are limited, and concordance of results across laboratories is unknown.

OBJECTIVES

This study aimed to determine inter-investigator agreement on the interpretation of FC results from split samples analyzed in different laboratories using various protocols, cytometers, and software; and on the interpretation of archived FC standard (FCS) data files contributed by the different investigators.

METHODS

This was a multicenter observational cross-sectional study. Anticoagulated blood or lymph node aspirate samples from nine client-owned dogs were aliquoted and shipped to participating laboratories. Samples were analyzed with individual laboratory-developed protocols. In addition, FCS files from a set of separate samples from 11 client-owned dogs were analyzed by participating investigators. A person not associated with the study tabulated the results and interpretations. Agreement of interpretations was assessed with Fleiss' kappa statistic.

RESULTS

Prolonged transit times affected sample quality for some laboratories. Overall agreement among investigators regarding the FC sample interpretation was strong (κ = 0.86 ± 0.19, P < .001), and for specific categories, ranged from moderate to perfect. Agreement of the lymphoproliferation or other leukocyte sample category from the analysis of the FCS files was weak (κ = 0.58 ± 0.05, P < .001).

CONCLUSIONS

Lymphoproliferations were readily identified by FC, but identification of the categories of hematolymphoid neoplasia in fresh samples or archived files was variable. There is a need for a more standardized approach to maximize the enormous potential of FC in veterinary medicine.

The Genetic and Molecular Basis for Canine Models of Human Leukemia and Lymphoma

Emerging details of the gene expression and mutational features of canine lymphoma and leukemia demonstrate areas of similarities and differences between disease subsets in the humans and dogs. Many features of canine diffuse large B-cell lymphoma resemble the ABC form of human DLBCL, including constitutive activation of the NF-kB pathway, and almost universal presence of double expressing MYC/BCL2 lymphomas. Frequent TRAF3 mutations and absence of BCL6 expression are differences with the human disease that need further exploration. Canine peripheral T-cell lymphoma is more common in dogs than in people and behaves in a similarly aggressive manner. Common features of canine and human PTCL include activation of the PI3 kinase pathways, loss of PTEN, and the tumor suppressor CDKN2. There is insufficient data available yet to determine if canine PTCL exhibits the GATA3-TBX21 dichotomy seen in people. Common to all forms of canine lymphoproliferative disease are breed-specific predilections for subsets of disease. This is particularly striking in PTCL, with the Boxer breed being dramatically overrepresented. Breed-specific diseases provide an opportunity for uncovering genetic and environmental risk factors that can aid early diagnosis and prevention.

B-cell chronic lymphocytic leukemia in a miniature American Eskimo dog

An 11-year-old neutered male miniature American Eskimo dog was presented for routine dental cleaning with moderately enlarged submandibular, prescapular, and popliteal lymph nodes. On pre-anesthetic blood analysis a moderate, poorly regenerative anemia and marked lymphocytosis were observed. Although cytologic evaluation of a lymph node aspirate was interpreted as lymphoma, a complete blood cell count, flow cytometric immunotyping of blood leukocytes, and serum electrophoresis identified B-cell chronic lymphocytic leukemia. Chemotherapy with chlorambucil was recommended.

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).

Protein characterization using electrophoresis and immunofixation; a case-based review of dogs and cats

Protein electrophoresis and immunotyping can be a useful adjunct to the standard biochemical techniques for characterizing serum and urine proteins. This paper reviews currently available and commonly used methods for diagnostic protein electrophoresis, including both agarose gel and capillary zone electrophoretic techniques and total protein assessments. Immunofixation and immunosubtraction methods for identification of immunoglobulin location and class are also presented. Practical application of quality assurance and quality control strategies in compliance with American Society of Veterinary Clinical Pathology (ASVCP) best practices are discussed. Commonly encountered serum and urine electrophoretic diagnostic patterns, including electrophoretically normal, acute-phase protein responses, polyclonal gammopathies, restricted polyclonal/oligoclonal gammopathies, paraproteinemias (monoclonal or biclonal gammopathies), and Bence-Jones proteinurias are also reviewed using relevant case material. Cases in which immunofixation electrophoresis are particularly useful are highlighted, and methodologies to more accurately quantify serum monoclonal proteins (M-proteins), monitoring tests commonly used in human medicine, are discussed.

CAR T Cell Immunotherapy in Human and Veterinary Oncology: Changing the Odds Against Hematological Malignancies

The advent of the genome editing era brings forth the promise of adoptive cell transfer using engineered chimeric antigen receptor (CAR) T cells for targeted cancer therapy. CAR T cell immunotherapy is probably one of the most encouraging developments for the treatment of hematological malignancies. In 2017, two CAR T cell therapies were approved by the US Food and Drug Administration: one for the treatment of pediatric acute lymphoblastic leukemia (ALL) and the other for adult patients with advanced lymphomas. However, despite significant progress in the area, CAR T cell therapy is still in its early days and faces significant challenges, including the complexity and costs associated with the technology. B cell lymphoma is the most common hematopoietic cancer in dogs, with an incidence approaching 0.1% and a total of 20-100 cases per 100,000 individuals. It is a widely accepted naturally occurring model for human non-Hodgkin's lymphoma. Current treatment is with combination chemotherapy protocols, which prolong life for less than a year in canines and are associated with severe dose-limiting side effects, such as gastrointestinal and bone marrow toxicity. To date, one canine study generated CAR T cells by transfection of mRNA for CAR domain expression. While this was shown to provide a transient anti-tumor activity, results were modest, indicating that stable, genomic integration of CAR modules is required in order to achieve lasting therapeutic benefit. This commentary summarizes the current state of knowledge on CAR T cell immunotherapy in human medicine and its potential applications in animal health, while discussing the potential of the canine model as a translational system for immuno-oncology research.

Preferential use of unmutated immunoglobulin heavy variable region genes in Boxer dogs with chronic lymphocytic leukemia

Human chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease, and immunoglobulin heavy variable region (IGHV) gene mutational status is an important prognostic marker. IGHV mutational status has not been previously examined in canine CLL. We sequenced the IGHV-D-J rearrangements from 55 canine patients with CLL, including 36 non-Boxer and 19 Boxer dogs. The majority of non-Boxers (75%) had mutated IGHV genes, whereas the majority of Boxers (79%) had unmutated IGHV genes. IGHV3-41 and IGHV3-67 gene usage was significantly higher in Boxers with CLL compared to non-Boxers. Additionally, 11 Boxers with large B-cell lymphoma and the normal IGHV repertoire of six control dogs (three Boxers and three non-Boxers) were sequenced. IGHV3-41 was preferentially used in Boxers with other forms of lymphoma and without lymphoproliferative disease. However, preferential use of unmutated IGHV genes was unique to Boxers with CLL, suggesting Boxers may be a valuable model to investigate unmutated CLL.

Increased frequency of CD45 negative T cells (T zone cells) in older Golden retriever dogs

T zone lymphoma (TZL) is characterized by the clonal expansion of T cells lacking expression of the pan-leukocyte antigen CD45 (TZ cells). A strong breed predisposition is observed in Golden retrievers. This study aimed to confirm aberrant CD45 mRNA expression and determine if Golden retrievers without clinical lymphoma have an increased frequency of circulating TZ cells. Gene expression analysis on confirmed TZL cases showed a significant decrease in CD45 expression compared to normal dogs. Peripheral blood samples from senior dogs, 242 Golden retrievers and 42 non-Golden retrievers, without evidence of lymphoproliferative disease were assessed for the presence of TZ cells by flow cytometry. Thirty-one percent of Golden retrievers had TZ cells compared to 14% of non-Golden retrievers. Thirty-four percent of Golden retrievers with TZ cells had a clonal T cell receptor gamma (TRG) gene rearrangement. Interestingly, 20% of Golden retrievers without TZ cells also had a clonal TRG rearrangement. Golden retrievers may have an increased risk of TZL due to an increased frequency of TZ cells.

Lymphoid Neoplasia: Correlations Between Morphology and Flow Cytometry

Cytology is commonly used to diagnose lymphoma and leukemia. Frequently, a diagnosis of lymphoproliferative disease can be obtained via cytology, and some of the common subtypes of canine lymphoma and leukemia can have characteristic cytologic features. Flow cytometry is a critical tool in the objective diagnosis and further characterization of lymphoma and leukemia. Features of the immunophenotype, such as expression of certain cell surface proteins or cell size, can provide important prognostic information. This review describes the cytologic features, flow cytometry immunophenotype, and immunophenotypic prognostic information for 6 major types of canine lymphoma and leukemia.