Progression of cutaneous plasmacytoma to plasma cell leukemia in a dog

Cutaneous plasmacytoma with Mott cell differentiation in a dog

Cytologic evaluation of aspirate slides from a small, <1-cm, interdigital mass on a 9-y-old, spayed female Yorkshire Terrier revealed a proliferation of discrete, round cells containing few-to-many, variably sized, round, eosinophilic, cytoplasmic inclusions. The top differentials based on the cytologic findings were either a plasma cell tumor or a B-cell lymphoma with Mott cell differentiation. The unencapsulated, well-demarcated, multilobulated round-cell neoplasm was completely excised. Immunohistochemical stains were performed to further characterize the neoplasm, which had immunolabeling for multiple myeloma oncogene 1 and vimentin, but did not react with CD3, CD20, melan A, or ionized calcium-binding adapter molecule 1, nor with a Giemsa special stain. Ultrastructurally, the cytoplasmic granules had Russell body-like morphology. A solitary, cutaneous plasmacytoma with Mott cell differentiation has not been described previously in veterinary medicine, to our knowledge.

Myocardial plasma cell tumor with intratumoral amyloidosis in a dog

A 12-year-old mixed breed dog was evaluated for marked hypercalcemia that was identified during assessment for acute polydipsia and polyuria. Physical examination identified a new grade II/VI left apical systolic murmur. A mass involving the left ventricular posterior wall and left atrium was identified by echocardiography, suggesting neoplastic invasion into the myocardium. The patient was euthanized, and post-mortem cardiac evaluation identified an intramyocardial amyloid-producing plasma cell tumor. Multiple myeloma was suspected but could not be confirmed due to the limited post-mortem evaluation. This case is the first report of myocardial amyloidosis in a dog with a myeloma-related disorder (MRD). Dogs with MRD and myocardial involvement may not exhibit clinical signs that localize to the cardiovascular system; therefore, echocardiography should be considered during the staging process.

A retrospective study of canine oral extramedullary plasmacytoma over a 15-year period (July 2004-July 2019): Treatment, histologic parameters and clinical outcomes

A total of 45 cases of canine oral extramedullary plasmacytomas (EMPs) presented to a tertiary referral institution over a 15-year period were examined. Histologic sections of 33 of these cases were examined for histopathologic prognostic indicators. Patients underwent variable treatment including surgical intervention, chemotherapy and/or radiation therapy. Long term survival was observed in the majority of dogs with a median survival time of 973 days (2-4315 days). However, almost 1/3 of dogs had progression of plasma cell disease, including two cases with myeloma-like progression. Histologic characterization of these tumours did not reveal criteria to predict tumour malignancy. However, cases without tumour progression did not exceed 28 mitotic figures in ten 400× fields (2.37 mm² ). All cases with tumour related death showed at least moderate nuclear atypia. Oral EMPs may represent a local manifestation of systemic plasma cell disease or singular focal neoplasia.

Myelomatous pleural effusion in a cat diagnosed with multiple myeloma

Case summary

A 10-year-old male castrated domestic shorthair cat was presented with a 3-day history of dyspnoea, chronic lethargy and inappetence. A bilateral pleural effusion was identified by thoracic ultrasound, and cytological examination revealed numerous atypical plasma cells. Biochemistry and serum protein electrophoresis revealed a severe hyperglobulinaemia associated with a monoclonal gammopathy. A moderate non-regenerative anaemia was also noted. Multiple bone lytic lesions were detected, and marked plasmacytosis was observed on bone marrow aspirates. Chemotherapy with cyclophosphamide and prednisolone was initiated but did not result in any clinical or biological response, and pleural effusion recurred. Lack of therapeutic response led to euthanasia 2 months after diagnosis.

Relevance and novel information

This is the first description of a myelomatous pleural effusion in a cat diagnosed with multiple myeloma and should be considered as one of the possible differential diagnoses for cats presented with pleural effusion and hyperglobulinaemia. The diagnostic, therapeutic and prognostic aspects of this manifestation are discussed.

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.

Multiple Myeloma with Skin and Renal Involvement and Anaplasma Phagocytophilum Co-Infection in a Dog

An 11-year-old male Cocker Spaniel was presented with acute onset of apathy, polyuria and polydipsia. Blood examination showed hypoalbuminemia and hyperglobulinemia, while electrophoresis revealed monoclonal gammopathy. Subsequent tests showed glycosuria, proteinuria, a positive serology test for Anaplasma spp. and ultrasonographical changes of the liver and spleen. Urine electrophoresis confirmed the presence of Bence-Jones protein. The dog’s condition deteriorated, and the dog had developed skin lesions on the neck and body. The owner decided to euthanize the dog and agreed to bone marrow and skin biopsy. Bone marrow cytology revealed an increased number of plasma cells and several cellular atypia. Histopathology of the skin lesions showed a round cell tumor of lymphoid or plasmacytoid origin. Subsequent immunohistology supported the diagnosis of multiple myeloma cutaneous involvement.

This case report describes unusual features observed in a dog with multiple myeloma.

Urinary bladder wall mass with neoplastic lymphoid cells in the urine: Diagnosis of an IgG secretory B-cell lymphoma with Bence-Jones proteinuria in a dog

In this study, we describe a multimodal approach to diagnose a unique case of myeloma-related disease, extranodal secretory B-cell lymphoma with urinary bladder involvement, an IgG4 monoclonal gammopathy, and Bence-Jones proteinuria in a dog with a 6-year history of hyperglobulinemia that had not been further evaluated. A 12-year-old dog was presented for evaluation of a 1-week history of tenesmus. Urine sediment cytologic evaluation revealed low to moderate numbers of intermediate to large-sized lymphocytes. We describe a technique that yielded adequate numbers of viable neoplastic cells in shipped urine sediment for PARR and flow cytometry. Those studies demonstrated a clonal immunoglobulin gene rearrangement and an expansion of CD21-positive and MHC Class II-negative B cells, respectively. Protein electrophoresis with immunofixation and proteomic evaluation revealed a serum and urine IgG4 monoclonal gammopathy with Bence-Jones proteinuria. MUM1 immunocytochemistry performed on the urine sediment slides failed to label the neoplastic cells; thus, a plasma cell tumor was considered unlikely. Lack of response to a cyclophosphamide, vincristine, and prednisone chemotherapy regimen led to euthanasia without necropsy 21 days after diagnosis. Lymphoma is the most common hematopoietic malignancy and accounts for up to a quarter of all neoplasms in dogs, but lymphoid neoplasms arising primarily from extranodal sites are infrequently reported. Urinary tract neoplasia can be diagnosed by urine evaluation in about one-third of canine cases, but the diagnosis of lymphoid neoplasia via urine evaluation is rarely reported. This case highlights the utility of ancillary diagnostics on urine for detection of lymphoid malignancies.

Atypical multiple myeloma in 3 young dogs

Three dogs under 12 months old were diagnosed with atypical multiple myeloma (MM), having an aggressive multifocal anaplastic round cell sarcoma in bone marrow, viscera, and/or peripheral blood, which were confirmed by cytology and immunohistochemistry to be of plasma cell origin. The intramedullary sarcomas caused myelophthisis, osteolysis, and hypercalcemia. Complete or free light chain monoclonal gammopathy in the serum and/or urine was demonstrated by protein electrophoresis and immunofixation. The polymerase chain reaction for antigen receptor rearrangement assay performed on 2 cases identified a clonally rearranged immunoglobulin gene. Neoplastic cells lacked expression of CD45, CD3, CD18, CD21, CD34, and MHCII by flow cytometry. Immunohistochemistry revealed MUM1 immunoreactivity of the neoplastic cells. Combining all data, the diagnosis was MM. An aggressive form of MM in young dogs should be a differential diagnosis for patients with an immunoglobulin-productive, B cell-clonal, CD45-negative, MUM1-positive discrete cell neoplasm arising from the bone marrow.

Morphology and Composition of Immunodiffusion Precipitin Complexes Evaluated via Microscopy and Proteomics

New approaches to rapid, simple, in vitro diagnostic immunoassays that do not rely on centralized laboratory facilities are urgently needed for disease diagnosis and to inform treatment strategies. The recent and ongoing COVID-19 pandemic has emphasized that rapid diagnostics are needed to help guide government policies on quarantines, social distancing measures, and community lockdowns. A common approach to developing new immunoassays is to modify existing platforms (e.g., automated ELISA and lateral flow assays) for the new analyte, even though this does not address the drawbacks of existing platforms. An alternate approach is to search for robust assays that have been superseded but could in fact solve important challenges using modern technologies. Immunodiffusion is one such platform based on unique "precipitin ring" patterns formed in gels or paper following interactions between proteins and cognate antibodies in diffusion/reaction systems. Herein, we investigate the microstructure of these precipitin rings using a combination of fluorescence and electron microscopy and also perform a mass spectrometry investigation to determine the proteomic composition of the rings. We observed that the rings were composed of microparticles, which we termed "precipitin complexes", and that these complexes were composed of at least 19 key proteins, including immunoglobulins and complement factors along with a range of plasma proteins, possibly related to immune complexes and/or high-density lipoprotein particles. This information will be useful in developing new in vitro diagnostics using reaction/diffusion systems-techniques that require a single assay step and that only require calibrated length measurements for target protein quantification.

Retrospective evaluation of the use of the International Myeloma Working Group response criteria in dogs with secretory multiple myeloma

BACKGROUND

Current recommendations for monitoring disease progression and response to treatment in humans with multiple myeloma include evaluation of serum paraprotein (M-protein) concentration. Densitometry, species-specific radial immunodiffusion (RID) and ELISA methods can be used to quantify M-proteins.

OBJECTIVE

Retrospectively evaluate use of the International Myeloma Working Group (IMWG) response criteria for humans in dogs with multiple myeloma.

ANIMALS

Sixteen dogs with a diagnosis of multiple myeloma, M-protein documented by serum protein electrophoresis (SPE) and immunofixation (IF) in an initial sample and subsequent electrophoretic evaluation of serial samples.

METHODS

Retrospectively, densitometric M-proteins, RID and globulins were measured and characterized according to IMWG criteria. Available clinical history was reviewed. Overall survival time (OST) was calculated from initial electrophoretic evaluation to death or last contact.

RESULTS

All cases received some form of nonstandardized chemotherapy. Complete response (CR), a lack of detectable M-protein by SPE and IF, was documented in 1 case. Median survival was longer for dogs that attained ≥90% densitometric M-protein reduction (630 days) than for those that did not attain at least 50% reduction in densitometric M-protein (284 days; log rank P = .006). Five dogs were defined as having progressive disease (M-protein increase of >25% and at least 0.5 g/dL from nadir), which correlated with concurrent or subsequent clinical deterioration. Response criteria categorized by serum globulins or RID was not correlated with OST or clinical findings.

CONCLUSIONS AND CLINICAL IMPORTANCE

Densitometric M-protein characterized using IMWG response criteria correlated with OST and clinical findings. Densitometric M-protein detection should be used to monitor dogs with multiple myeloma.

Chromogenic in situ hybridization for the detection of lambda and kappa immunoglobulin light chains as a potential auxiliary diagnostic technique in canine plasmacytomas

The heterogeneous morphologic features of canine plasmacytomas (PCTs) can make their differentiation from other round cell tumors challenging. Immunohistochemistry (IHC) for lambda (λ) and kappa (к) immunoglobulin (Ig) light chains is often equivocal because of high background staining. The chromogenic in situ hybridization (CISH) technique for light chains has shown higher sensitivity compared to IHC in human plasma cell tumors. Therefore, we aimed to validate automated CISH for light chains in canine tissues and to evaluate its diagnostic potential in canine PCTs, in conjunction with routinely used IHC markers. CISH for light chains demonstrated a clear signal in plasma cell populations of canine control tissues (lymph nodes, lymphoplasmacytic inflammation) showing a polyclonal pattern with a prevalence of λ-producing cells. CISH detected monotypic light chain expression in 33 of 53 (62%) PCTs, 31 expressing λ and 2 expressing к. CISH was more sensitive than IHC for λ light chain (58% vs. 47%, respectively) and more easily interpretable given the absence of confounding background staining. The absence of CISH staining for both λ and к in a considerable subset of tumors may be the result of lower light chain production by neoplastic cells. Multiple myeloma oncogene 1 (MUM1) was expressed by all but 2 PCTs (96%), which showed λ expression by CISH and IHC. The identification of poorly differentiated canine PCTs requires the assessment of a panel of IHC markers, with the potential support of CISH for Ig light chains.

Pathologic and flow cytometric features of a case of canine ventral cervical lymphangiosarcoma

An 11-y-old spayed female German Shepherd was presented for a second opinion of ventral cervical swelling of 3-mo duration. On examination, the dog had significant dependent ventral cervical swelling. Enlarged lymph nodes with cystic changes and severe edematous facial swelling were noted on computed tomography. Fine-needle aspiration of the ventral cervical swelling revealed yellow-tinged fluid, with a predominance of lymphoid cells noted on cytologic examination. On cervical exploratory surgery, the left mandibular lymph node was surrounded by a large fluid pocket; biopsies of the lymph node were obtained. Impression smear cytology, flow cytometry, PCR for antigen receptor gene rearrangements, and histopathology were performed on samples from the left mandibular lymph node. Impression smear cytology revealed a population of atypical discrete cells. Flow cytometry identified a population of CD34+/CD45- large cells. A tumor of endothelial origin within the medulla of the lymph node was identified by histopathology, and lymphangiosarcoma was confirmed based on prospero-related homeobox gene 1 (PROX1) immunoreactivity. Our study describes the challenges in the diagnosis of a rarely reported entity and highlights that neoplastic endothelial cells should be considered as a differential when high proportions of CD34+/CD45- cells are present in flow cytometry.

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.

Multiple cutaneous plasmacytosis with multilobated (clover-leaf shaped) nuclei cells in a dog

A 12‐year‐old female Shih‐tzu dog was presented with a 2‐month history of cutaneous non‐pruritic multiple ulcerated or crusted nodules of less than 1.5 cm in diameter on eyelids, lips, abdomen, groin, thighs and perianal region. Several diagnostic tests were performed, including fine needle aspiration and skin biopsy of the cutaneous nodules. Cytologic interpretation was round cell neoplasm with multilobated (clover‐leaf shaped) nuclei. Histopathology revealed round neoplastic cells with prominent anisocytosis and anisokaryosis, and numerous mitotic figures; however, the origin of the cells was not identified. Immunohistochemical evaluation indicated that these cells were positive for CD79a and MUM‐1, but negative for CD3, CD20 and Pax 5. The patient was treated with chemotherapy, and the skin condition improved. Despite good response to chemotherapy, the patient was euthanized due to poor general health.

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.

Plasma cell leukemia with plasmablastic morphology in a dog

A 5-y-old female Golden Retriever was presented with a 2-wk history of hyporexia, vomiting, diarrhea, lethargy, weight loss, polyuria, and polydipsia. Clinical examination and ultrasonography revealed multiple organ enlargement with gallbladder and kidney nodules suggestive of disseminated neoplasia. Hematologic and biochemical analyses revealed pancytopenia, hypercalcemia, and monoclonal IgA gammopathy suspicious for a plasma cell neoplasm. Bone marrow and blood smear examination revealed neoplastic atypical cells highly suggestive of lymphoid origin. Autopsy confirmed the presence of homogeneous white masses and multifocal pale infiltrates in the spleen, kidney, small intestine, gallbladder, and urinary tract. Histologic features were consistent with a multicentric atypical plasma cell tumor. Tumor cells were negative for CD204, IBA-1, E-cadherin, CD3, CD5, CD79a, CD20, and PAX5, and positive for MUM1, consistent with plasma cell origin. The presence of > 20% of circulating blastic plasma cells was consistent with primary plasma cell leukemia with plasmablastic morphology, a disease rarely described in veterinary medicine.

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.

Cytology and the cell block method in diagnostic characterization of canine lymphadenopathy and in the immunophenotyping of nodal lymphoma

Minimally invasive techniques used to evaluate canine peripheral lymphadenopathy (PLN), including fine needle aspiration biopsy with cytological evaluation (FNAB-C) and flow cytometry (FC), have benefits and limitations. The cell block (CB) method is an alternate processing technique in which fine needle aspirate biopsy samples are concentrated, fixed, and embedded in paraffin for routine histological processing/staining. Utilizing three observers, we determined the diagnostic value of the CB in evaluating canine PLN across six categories (non-diagnostic, reactive, inflammatory/infectious, probable lymphoma and lymphoma, metastatic neoplasia) and correlated findings to immunophenotypic and clonal antigen receptor rearrangement results in canine nodal lymphoma. Eighty-five paired FNAB-C and CB samples were evaluated from canine patients presenting to the University of Minnesota Veterinary Oncology or Internal Medicine services. Diagnostic quality samples were obtained in 55/85 (65%) CB and 81/85 (95%) FNAB-C samples, respectively, and nodal pathology impacted CB diagnostic yield. Overall percent agreement between diagnostic-quality FNAB-C and CB samples was 86%, but increased to 95% if the categories of lymphoma and probable lymphoma were combined. There was 100% agreement for both the diagnoses of metastatic neoplasia and reactive lymph nodes and 92% agreement for the diagnosis of lymphoma/probable lymphoma. Using immunohistochemistry (IHC), CB samples correctly immunophenotyped 22/23 (96%) cases of B-cell lymphoma, but only 1/6 (17%) cases of T-cell lymphoma. IHC was not completed on nine cases of lymphoproliferative disease because of insufficient cellularity. When the CB method (CBM) yielded diagnostic quality samples there was good to excellent agreement with FNAB-C samples and CB samples were suitable for some IHC tests.

PCR-based clonality analysis of antigen receptor gene rearrangements in canine cutaneous plasmacytoma

Plasmacytomas are discrete, B cell-derived, round cell tumours that sometimes are difficult to distinguish from canine cutaneous histiocytomas or T cell lymphosarcomas (lymphomas). Diagnosis of plasmacytomas relies on morphological observations and immunohistochemistry for multiple myeloma oncogene-1 (MUM-1) and cluster of differentiation 3 (CD3). Clonality testing often is used as an adjunct diagnostic tool to examine lymphoproliferative diseases. In this study, the sensitivity of PCR-based clonality analysis of antigen receptor gene rearrangements in canine cutaneous plasmacytomas was determined. Formalin-fixed paraffin-embedded sections of 29 canine plasmacytomas, 23 diffuse large B cell lymphomas (DLBCLs) and 23 lymph nodes without lymphoma were used for clonality analysis. New oligonucleotide primers for the framework (FR)2 and FR3 regions of the immunoglobulin heavy chain (IGH) V gene subgroup 3 were designed and used with previously reported FR3 primers. Although plasma cells are of B cell lineage, the detected frequency of IGH clonality in plasmacytoma was 0-34.5% with the seven primers used, whereas in DLBCLs it was 8.7-78.3%. In 23 lymph nodes without lymphoma, IGH clonality was detected in only one case with two out of the seven primers used. Sequence analysis of PCR products from plasmacytomas revealed mismatches in the annealing region of the FR3 primers. The sensitivity of detecting IGH clonality in canine plasmacytomas was lower than in DLBCLs. The low detection rate of IGH clonality in canine plasmacytoma may be due to somatic hypermutation of the variable region.

Metastatic thymoma in the liver of a dog

A 12-y-old neutered male Portuguese Water dog was presented because of a 1-y history of persistent hyporexia, diarrhea, and recurrent pyelonephritis. Abdominal ultrasound revealed hepatic nodules and diffuse splenomegaly, and radiographs revealed a mediastinal mass. Fine-needle aspirates of the liver, spleen, and mediastinal mass were suspicious for lymphoma. Flow cytometry identified small T cells that co-expressed CD4 and CD8 at all sites, most suspicious for thymoma, but lymphoma could not be ruled out. PCR for antigen receptor rearrangements analysis identified polyclonal amplification of the T-cell receptor genes, more consistent with thymoma than lymphoma. Histopathology of the liver and thymic mass confirmed thymoma with hepatic metastasis.

Indolent T-cell-rich small B-cell hepatic lymphoma in a Golden Retriever

An 11-year-old female spayed Golden Retriever presented for an incidentally found liver mass. The hepatic mass and intra-abdominal lymph nodes had a marked heterogeneous T-cell population and far fewer numbers of small clonal B cells. This T-cell-rich small B-cell lymphoma had a unique histological pattern and indolent clinical course.

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.