Spindle cell cutaneous epitheliotropic T-cell lymphoma in an American Bulldog

An 8-year-old American Bulldog developed coalescing exophytic bulbous nodules that grew rapidly on the left pinna and a single cutaneous mass on the left flank. Histological examination of the pinnal biopsy by a diagnostic laboratory revealed a densely cellular neoplasm with haphazardly arranged round to spindle cells with high mitotic activity and epitheliotropism. The initial diagnosis was a poorly differentiated malignant neoplasm with differential diagnoses including melanoma, tumour of histiocytic origin and, less likely, a pleomorphic lymphoma. A panel of melanoma immunohistochemical markers and immunolabelling for CD18 were pursued. Neoplastic cells were immunopositive for CD18 but negative for Melan-A, PNL2, TRP-1 and TRP-2, suggestive of a histiocytic tumour or lymphoma. The left ear masses recurred, and more masses developed on the body. The pinnectomized ear was submitted to the University of Missouri Veterinary Medical Diagnostic Laboratory. Similar cells were seen and were immunolabelled for CD18 and CD3 but were immunonegative for SOX10, CD79a and CD20. PCR for antigen receptor rearrangements revealed a clonal rearrangement of T-cell receptor gamma. These findings enabled a final diagnosis of epitheliotropic T-cell lymphoma with spindle cell morphology. Lymphoma should be considered as a potential differential diagnosis for cutaneous nodules of spindle cell morphology and lymphocytic immunohistochemical markers should be included in diagnostic panels.

Plasma cell-free DNA in canine lymphoma patients as a novel material for genotyping

Canine lymphoma is a disease with high morbidity and poor long-term prognosis, despite a high response rate to chemotherapy. In this study, we focused on liquid biopsy, in which small amounts of substances from body fluids were analysed, to determine whether cell-free DNA (cfDNA) in the plasma can be used as a biomarker for lymphoma in dogs. We found that 23 patients with lymphoma had significantly higher cfDNA concentrations than the 12 healthy dogs (median 2360 ng/mL versus 299 ng/mL, p < .0001). Polymerase chain reaction for antigen receptor rearrangement (PARR) was also employed using cfDNA from the lymphoma group to investigate whether cfDNA could be used for the detection of genetic clonality of lymphomas, as well as the genomic DNA (gDNA) extracted from an original lesion in each case. The correlation of the PARR results between cfDNA and gDNA was observed in 100% of B-cell lymphomas (10/10), 77.8% of T-cell lymphomas (7/9), and 100% of other types of lymphomas (4/4), respectively. These results indicate that plasma cfDNA levels are increasing in canine lymphoma patients, that cfDNA concentration can be a novel diagnostic tool, and that it can be used as a diagnostic tool for PARR.

Characterization of CD3+/CD20+ canine large-cell lymphoma

Immunophenotyping of canine large-cell lymphoma (LCL) for B-cell and T-cell surface antigens is commonly performed to better predict the clinical outcome. Expression of surface antigen CD3 is associated with T-cell malignancies; surface antigen CD20 is expressed on B cells. However, a small subset of canine LCLs expresses both CD3 and CD20 (CD3+/CD20+); this form of lymphoma remains poorly defined at the molecular level. In a retrospective study, we aimed to better characterize immunophenotypic properties and antigen receptor clonality of CD3+/CD20+ LCL. We selected formalin-fixed, paraffin-embedded tissues from 10 cases of CD3+/CD20+ LCL and breed-matched controls of peripheral large T-cell lymphoma (PTCL) and diffuse large B-cell lymphoma (DLBCL). Using PCR for antigen receptor rearrangement (PARR), we identified monoclonal T-cell receptor gamma (TCRγ) rearrangements in all CD3+/CD20+ cases. Three of 10 cases had monoclonal rearrangements in the immunoglobulin heavy chain (IgH), supportive of cross-lineage rearrangement. There was no significant difference in the frequency of antigen receptor rearrangement between CD3+/CD20+ and PTCL cases. In comparison with DLBCL, CD3+/CD20+ LCL had TCRγ rearrangement more frequently and IgH rearrangement less frequently, respectively. Immunolabeling of the B-cell marker PAX5 occurred less frequently in all CD3+/CD20+ LCL cases compared to the DLBCL controls. Immunolabeling for BCL-2 was robust, regardless of immunophenotype. Nuclear Ki67 positivity was variable in CD3+/CD20+ cases, indicating a heterogeneity in proliferation. Overall, cases of canine CD3+/CD20+ LCL had properties similar to PTCL, suggesting a similar histogenesis of these 2 subsets.

Canine Somatic Mutations from Whole-Exome Sequencing of B-Cell Lymphomas in Six Canine Breeds-A Preliminary Study

Canine lymphoma (CL) is one of the most common malignant tumors in dogs. The cause of CL remains unclear. Genetic mutations that have been suggested as possible causes of CL are not fully understood. Whole-exome sequencing (WES) is a time- and cost-effective method for detecting genetic variants targeting only the protein-coding regions (exons) that are part of the entire genome region. A total of eight patients with B-cell lymphomas were recruited, and WES analysis was performed on whole blood and lymph node aspirate samples from each patient. A total of 17 somatic variants (GOLIM4, ITM2B, STN1, UNC79, PLEKHG4, BRF1, ENSCAFG00845007156, SEMA6B, DSC1, TNFAIP1, MYLK3, WAPL, ADORA2B, LOXHD1, GP6, AZIN1, and NCSTN) with moderate to high impact were identified by WES analysis. Through a Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of 17 genes with somatic mutations, a total of 16 pathways were identified. Overall, the somatic mutations identified in this study suggest novel candidate mutations for CL, and further studies are needed to confirm the role of these mutations.

Large granular lymphocyte lymphoma with leukemic phase and suspicion of leptomeningeal lymphomatosis in a cat - a case report

INTRODUCTION

In this case report we present a feline large granular lymphocyte (LGL) lymphoma, a rare morphologically distinct subtype of lymphoma, in a twelve-year-old female spayed domestic short hair cat, with high suspicion of leptomeningeal lymphomatosis due to magnetic resonance imaging findings and results of cerebral spinal fluid analyses. Diagnosis of LGL lymphoma was confirmed by means of blood cytology and polymerase chain reaction for antigen receptor rearrangements.

T-cell-rich, large B-cell lymphoma in the brain of a horse

T-cell-rich, large B-cell lymphoma (TCRLBCL) is the most commonly diagnosed type of lymphoma in horses. Here we describe the clinical signs, neuropathology, immunohistochemistry (IHC), and PCR for antigen receptor rearrangement (PARR) analysis results of a TCRLBCL in the brain of an 8-y-old male Quarter Horse that was euthanized after acute anorexia, tremors, head pressing, falling, blindness, incoordination, and seizures. Autopsy revealed a firm, smooth, pale-yellow mass that expanded both lateral ventricles and the adjacent subcortical white matter. Histologically, the mass consisted of a densely cellular neoplasm composed of large, CD79+ neoplastic B-lymphocytes admixed with sheets of small, CD3+ reactive T-lymphocytes, Iba1+ histiocytes, MUM1+ plasma cells, and rare eosinophils supported by a fine fibrovascular stroma. Formalin-fixed, paraffin-embedded tissue scrolls were retrieved and subjected to PARR analysis, which revealed a clonal reaction in the immunoglobulin gene and a polyclonal reaction for the T-lymphocyte receptor gene, consistent with a neoplastic B-lymphocyte and reactive T-lymphocyte proliferation. The diagnosis of TCRLBCL was suspected histologically and confirmed based on IHC and PARR analysis.

A Message Passing-Assisted Iterative Noise Cancellation Method for Clipped OTFS-BFDM Systems

Compared with orthogonal frequency division multiplexing (OFDM) systems, orthogonal time frequency space systems based on bi-orthogonal frequency division multiplexing (OTFS-BFDM) have lower out-of-band emission (OOBE) and better robustness to high-mobility scenarios, but suffer from a higher peak-to-average ratio (PAPR) in large data packets. In this paper, one-iteration clipping and filtering (OCF) is adopted to reduce the PAPR of OTFS-BFDM signals. However, the extra noise introduced by the clipping process, i.e., clipping noise, will distort the desired signal and increase the bit error rate (BER). We propose a message passing (MP)-assisted iterative cancellation (MP-AIC) method to cancel the clipping noise based on the traditional MP decoding at the receiver, which incorporates with the (OCF) at the transmitter to keep the sparsity of the effective channel matrix. The main idea of MP-AIC is to extract the residual signal fed to the MP detector by iteratively constructing reference clipping noise at the receiver. During each iteration, the variance of residual signal and channel noise are taken as input parameters of MP decoding to improve the BER. Moreover, the convergence probability of the modulation alphabet after MP decoding in the current iteration is used as the initial probability of MP decoding in the next iteration to accelerate the convergence rate of MP decoding. Simulation results show that the proposed MP-AIC method significantly improves MP-decoding accuracy while accelerating the BER convergence in the clipped OTFS-BFDM system. In the clipped OTFS-BFDM system with rectangular pulse shaping, the BER of MP-AIC with two iterations can be reduced by 72% more than that without clipping noise cancellation.

Feline and Canine Cutaneous Lymphocytosis: Reactive Process or Indolent Neoplastic Disease?

Cutaneous lymphocytosis (CL) is an uncommon and controversial lymphoproliferative disorder described in dogs and cats. CL is generally characterized by a heterogeneous clinical presentation and histological features that may overlap with epitheliotropic lymphoma. Therefore, its neoplastic or reactive nature is still debated. Here, we describe clinicopathological, immunohistochemical, and clonality features of a retrospective case series of 19 cats and 10 dogs with lesions histologically compatible with CL. In both species, alopecia, erythema, and scales were the most frequent clinical signs. Histologically, a dermal infiltrate of small to medium-sized lymphocytes, occasionally extending to the subcutis, was always identified. Conversely, when present, epitheliotropism was generally mild. In cats, the infiltrate was consistently CD3+; in dogs, a mixture of CD3+ and CD20+ lymphocytes was observed only in 4 cases. The infiltrate was polyclonal in all cats, while BCR and TCR clonal rearrangements were identified in dogs. Overall, cats had a long-term survival (median overall survival = 1080 days) regardless of the treatment received, while dogs showed a shorter and variable clinical course, with no evident associations with clinicopathological features. In conclusion, our results support a reactive nature of the disease in cats, associated with prolonged survival; despite a similar histological picture, canine CL is associated with a more heterogeneous lymphocytic infiltrate, clonality results, and response to treatment, implying a more challenging discrimination between CL and CEL in this species. A complete diagnostic workup and detailed follow-up information on a higher number of cases is warrant for dogs.

Histopathologic, phenotypic, and molecular criteria to discriminate low-grade intestinal T-cell lymphoma in cats from lymphoplasmacytic enteritis

BACKGROUND

Differentiation of low-grade intestinal T-cell lymphoma (LGITL) from lymphoplasmacytic enteritis (LPE) in cats is a diagnostic challenge for pathologists.

OBJECTIVE

Characterize histologic, immunohistochemical, and molecular features of LGITL and LPE.

ANIMALS

Forty-four client-owned cats, 22 diagnosed with LGITL and 22 with LPE.

METHODS

Prospective, cohort study. Clinical suspicion of LGITL or LPE was based on persistent gastrointestinal signs, unresponsive to empirical treatments. All cats underwent a standardized diagnostic evaluation, including biopsy (preferentially full-thickness), and were diagnosed with LGITL or LPE after review of clinical, laboratory, sonographic, histologic, immunohistochemical, and clonality results.

RESULTS

A monomorphic lymphocytic population (22/22, 100%) and in-depth mucosal infiltration (15/22, 68%) were hallmarks of LGITL. Epithelial patterns (nests and plaques) were significantly more frequent in LGITL (11/22, 50%) than in LPE (1/22, 5%) cases (P = .001). A CD3+ lymphocytic apical-to-basal gradient was observed in 9/22 (41%) of LGITL vs 1/22 (5%) of LPE cases (P = .004). Most LPE cases (17/18, 94%) featured marked fibrosis in the superficial part of the lamina propria. The Ki-67 20%- and 30%-thresholds discriminated between LGITL and LPE within both the epithelium (specificity >95%) and lamina propria (specificity >95%), respectively. All LGITL cases were CD3+ pSTAT3- and pSTAT5+. T-cell receptor gamma chain gene rearrangements indicated monoclonality in 86% of LGITL cases. Surprisingly, 70% of LPE cases featured monoclonality (40%) or monoclonality on a polyclonal background (30%).

CONCLUSIONS AND CLINICAL IMPORTANCE

We identified new histologic, immunohistochemical, and clonality criteria to distinguish LGITL from LPE.

Revisiting lymphocyte clonality testing in feline B-cell lymphoma

Differentiation between resident mature lymphocyte populations and small-cell lymphoma cannot be made by cytological review alone and remains challenging in histopathological review. These cases warrant application of complementary tools like PCR-based immunoglobulin (IG) and T-cell receptor (TCR) clonality testing for confirmation. Although primer coverage of potential IG gene rearrangements in feline B-cell neoplasms constantly improves, the possibility of false negative and false positive test results still poses a problem. In this retrospective study, we assessed diagnostic sensitivity and specificity of a novel developed multiplex PCR assay for routine diagnosis of B-cell clonality. Therefore, 24 feline patients were subjected to comparative clonality testing by using different primer sets. Feline lymphoma cell lines and confirmed patient material served as positive control. Compared to previous studies, this novel developed multiplex PCR assay showed positive effects on diagnostic sensitivity, specificity, accuracy, and positive predictive value accompanied by a slight impairment of negative predictive value. Notably, none of the primer sets was superior; hence, we recommend the combined application of the herein tested primer sets in routine diagnostics. However, a more in-depth-evaluation of the dynamic of assay specific parameters in dependency on primer set usage requires prospective studies on larger cohorts of feline patients.

Composition of lymphocyte subpopulations in normal and mildly reactive peripheral lymph nodes in cats

OBJECTIVES

Flow cytometric (FCM) immunophenotyping of lymphoid tissue aspirates is an available adjunct for feline lymphoma diagnostics. Reference data have only been established for feline peripheral blood. Studies investigating the composition of normal and mildly reactive feline lymph nodes (LNs) are lacking. The aim of this prospective study was to establish reference data for lymphocyte subpopulations in normal and mildly reactive feline peripheral LNs using a standardised multicolour panel of antibodies.

METHODS

Macroscopically inconspicuous mandibular and/or popliteal LNs from 31 adult cats, which were euthanased for reasons other than haematological diseases, were excised and processed within 5 h after death. Multicolour flow cytometry using eight different feline-specific, anti-canine and human cross-reactive monoclonal antibodies used in current diagnostic marker panels was performed after cytological exclusion of pathological states and complemented by lymphocyte clonality testing, histopathology and immunohistochemistry (IHC) to ensure the absence of lymphoid disease.

RESULTS

Of 31 cats, the immunophenotyping data of 24 individuals could be included as histopathology and clonality testing excluded a pathological condition. Lymphocyte populations showed the following positive antibody reactions: CD18⁺ 86.3% ± 13.86%, CD3⁺ 54.81% ± 11.10%, CD5⁺ 57.39% ± 12.66%, CD21⁺ 40.42% ± 12.40%, CD79alphacy⁺ (CD79αcy) 30.41% ± 13.49% and CD14⁺ 0.75% ± 1.35%. There were 30.88% ± 13.48% CD4⁺ and 12.91% ± 6.68% CD8⁺ cells. Cytology revealed a mixed population of mostly lymphoid cells in all samples. The absence of a monoclonal/oligoclonal neoplastic population was confirmed by lymphocyte clonality testing. Histopathology and IHC showed a normal or mildly reactive pattern in all cases.

CONCLUSIONS AND RELEVANCE

This study establishes FCM immunophenotyping data of lymphocyte populations of normal and mildly reactive feline peripheral LNs. For the first time, anti-CD5, CD4, CD8 and CD21 reference data in normal and mildly reactive feline peripheral LNs are presented. CD18, CD3, CD14 and CD79αcy have been used to establish reference data for the first time in any feline material.

Tumor staging in a Beagle dog with concomitant large B-cell lymphoma and T-cell acute lymphoblastic leukemia

An 8-y-old spayed female Beagle dog was presented with peripheral lymphadenomegaly. Lymph node cytology and flow cytometry led to the diagnosis of large B-cell lymphoma (LBCL). We detected minimal percentages of LBCL cells in peripheral blood and bone marrow samples. However, a monomorphic population of neoplastic cells different from those found in the lymph node was found in the bone marrow. T-cell acute lymphoblastic leukemia was suspected based on flow cytometric immunophenotyping. PCR for antigen receptor rearrangement (PARR) revealed clonal rearrangement of both B-cell and T-cell receptors, and the presence of both neoplastic clones in the lymph node, peripheral blood, and bone marrow. The dog was treated with multi-agent chemotherapy but died 46 d following diagnosis. Tumor staging and patient classification are needed to accurately establish a prognosis and select the most appropriate therapeutic protocol.

Comprehensive comparison of upper and lower endoscopic small intestinal biopsy in cats with chronic enteropathy

Background

Integrating immunohistochemistry (IHC) and clonality testing with histopathology may improve the ability to differentiate inflammatory bowel disease (IBD) and alimentary small cell lymphoma (LSA) in cats.

Hypothesis/Objectives

To evaluate the utility of histopathology, IHC, and clonality testing to differentiate between IBD and LSA and agreement of diagnostic results for endoscopic biopsy (EB) samples from the upper (USI) and lower small intestine (LSI).

Animals

Fifty‐seven cats with IBD or LSA.

Methods

All cases were categorized as definitive IBD (DefIBD), possible LSA (PossLSA), probable LSA (ProbLSA), or definitive LSA (DefLSA) based on histopathology alone. Results from IHC and clonality testing were integrated.

Results

Based on histopathology alone, 24/57 (42.1%), 15/57 (26.3%), and 18/57 (31.6%) cats were diagnosed with DefIBD, PossLSA or ProbLSA, and DefLSA, respectively. After integrating IHC and clonality testing, 11/24 cases (45.8%) and 15/15 cases (100%) previously categorized as DefIBD and PossLSA or ProbLSA, respectively, were reclassified as LSA. A final diagnosis of IBD and LSA was reported in 13/57 (22.8%) and 44/57 (77.2%) cats, respectively. Agreement between USI and LSI samples was moderate based on histopathology alone (κ = 0.66) and after integrating IHC and clonality testing (κ = 0.70). However, only 1/44 (2.3%) of the LSA cases was diagnosed based on LSI biopsy alone.

Conclusions and Clinical Importance

Integrating IHC and clonality testing increased the number of cases diagnosed with LSA, but the consequence for patient outcome is unclear. There was moderate agreement between USI and LSI samples. Samples from the LSI rarely changed the diagnosis.

First-time application of a PCR-based clonality assay in a large cohort of non-domestic felines

Feline lymphoma, one of the most important malignant tumors in domestic cats, is also increasingly diagnosed in non-domestic felines, most notably, African lions (Panthera leo). The gold standard for the diagnosis of lymphoma is histopathological evaluation. As an additional tool, the PCR for antigen receptor gene rearrangement (PARR) has been established. To support the diagnosis on a molecular level, the PCR-based clonality assay is designed to distinguish between reactive and neoplastic lymphocyte populations. In general, PARR primers are used to target complete immunoglobulin heavy chain V-D-J (IGH-VDJ) and T-cell receptor gamma V-J (TRG-VJ) chain gene rearrangements. In this study, we validated the primer sets used in routine diagnostics of domestic cats for the application in non-domestic felines. Clonality testing was used in 41 non-domestic feline species and the results were interpreted in the light of their clinical history and their pathology. In total, clonality could be detected in 8 non-domestic felines (19.4%), including 3 lymphoma cases confirmed by histopathology. These results confirmed the successful application of domestic feline-specific PARR primers in non-domestic feline species. Diagnostic sensitivity and specificity of the clonality assay were 100% and 88%, respectively. Finally, the overall diagnostic accuracy was 89%.

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.

A case of T-cell chronic lymphocytic leukemia progressing to Richter syndrome with central nervous system involvement in a dog

An 8-year-old neutered Beagle dog was presented with polyuria and polydipsia. Routine clinicopathologic testing showed a significant lymphocytosis and proteinuria. Lymphocytes were of small to intermediate in size with a mature morphology. Infectious disease screening was negative. PCR for antigen receptor gene rearrangements showed a clonal T-cell receptor (TCR) rearrangement consistent with T-cell chronic lymphocytic leukemia (CLL). Bone marrow cytology showed <30% lymphocytes, while the proportion in splenic fine-needle aspirate cytology was considered increased. The dog was initially monitored but started on prednisolone and chlorambucil therapy 2 months later due to worsening clinical signs and progressive lymphocytosis. After an additional 2 weeks, the dog developed multifocal spinal pain and single-node lymphadenomegaly. Cytology of the lymph node showed a monomorphic population of large lymphoblasts consistent with lymphoma. Cytology of a cerebrospinal fluid sample also showed large lymphoblasts. PCR for antigen receptor gene rearrangement at both sites showed a clonal TCR rearrangement of the same molecular size as in the initial leukemic cells. The dog was diagnosed with a transformation of the CLL to Richter syndrome (RS) with involvement of the central nervous system (CNS). Therapy was started with L-asparaginase and an increased dose of prednisolone; however, the dog was euthanized due to progressive clinical signs. To our knowledge, this is the first report of canine RS with direct involvement of the CNS.

Differentiation of lymphocytic-plasmacytic enteropathy and small cell lymphoma in cats using histology-guided mass spectrometry

BACKGROUND

Differentiation of lymphocytic-plasmacytic enteropathy (LPE) from small cell lymphoma (SCL) in cats can be challenging.

HYPOTHESIS/OBJECTIVE

Histology-guided mass spectrometry (HGMS) is a suitable method for the differentiation of LPE from SCL in cats.

ANIMALS

Forty-one cats with LPE and 52 cats with SCL.

METHODS

This is a retrospective clinicopathologic study. Duodenal tissue samples of 17 cats with LPE and 22 cats with SCL were subjected to HGMS, and the acquired data were used to develop a linear discriminate analysis (LDA) machine learning algorithm. The algorithm was subsequently validated using a separate set of 24 cats with LPE and 30 cats with SCL. Cases were classified as LPE or SCL based on a consensus by an expert panel consisting of 5-7 board-certified veterinary specialists. Histopathology, immunohistochemistry, and clonality testing were available for all cats. The panel consensus classification served as a reference for the calculation of test performance parameters.

RESULTS

Relative sensitivity, specificity, and accuracy of HGMS were 86.7% (95% confidence interval [CI]: 74.5%-98.8%), 91.7% (95% CI: 80.6%-100%), and 88.9% (95% CI: 80.5%-97.3%), respectively. Comparatively, the clonality testing had a sensitivity, specificity, and accuracy of 85.7% (95% CI: 72.8%-98.7%), 33.3% (95% CI: 14.5%-52.2%), and 61.5% (95% CI: 48.3%-74.8%) relative to the panel decision.

CONCLUSIONS AND CLINICAL IMPORTANCE

Histology-guided mass spectrometry was a reliable technique for the differentiation of LPE from SCL in duodenal formalin-fixed paraffin-embedded samples of cats and might have advantages over tests currently considered state of the art.

Composite lymphoma of concurrent T zone lymphoma and large cell B cell lymphoma in a dog

Background

Evolution of indolent to aggressive lymphoma has been described in dogs but is difficult to distinguish from the de novo development of a second, clonally distinct lymphoma. Differentiation of these scenarios can be aided by next generation sequencing (NGS)-based assessment of clonality of lymphocyte antigen receptor genes.

Case presentation

An 8-year-old male intact Mastiff presented with generalized lymphadenomegaly was diagnosed with nodal T zone lymphoma (TZL) based on cytology, histopathology, immunohistochemistry and flow cytometry. Thirteen months later, the dog re-presented with progressive lymphadenomegaly, and based on cytology and flow cytometry, a large B cell lymphoma (LBCL) was diagnosed. Sequencing-based clonality testing confirmed the de novo development of a LBCL and the persistence of a TZL.

Conclusions

The occurrence of two distinct lymphoid neoplasms should be considered if patient features and tumor cytomorphology or immunophenotype differ among sequential samples. Sequencing-based clonality testing may provide conclusive evidence of two concurrent and distinct clonal lymphocyte populations, termed most appropriately “composite lymphoma”.

Results of histopathology, immunohistochemistry, and molecular clonality testing of small intestinal biopsy specimens from clinically healthy client-owned cats

Background

Histopathology, immunohistochemistry, and molecular clonality testing are metrics frequently used to diagnose chronic enteropathy (CE) in cats. However, normal values for these metrics have been based mainly on samples from cats that were relatively young, specific pathogen‐free, or both.

Objectives

To describe results of histopathology, immunohistochemistry, and clonality testing of endoscopically‐derived biopsy specimens of the upper small intestinal tract from a cohort of clinically healthy client‐owned cats.

Animals

Twenty clinically healthy client‐owned cats ≥3 years of age.

Methods

Tissue specimens were collected from the stomach and duodenum and evaluated single blinded by a board‐certified pathologist. In addition, samples were evaluated by routine immunohistochemistry and clonality testing. Cats were followed after the procedure for signs of CE.

Results

Integrated results from histopathology, immunohistochemistry, and clonality testing were interpreted as consistent with small cell lymphoma (SCL; n = 12), emerging SCL (n = 1), lymphocytic enteritis (n = 6), and pseudoclonality (n = 1). On follow‐up, 3 cats eventually developed clinical signs of CE, of which 2 were euthanized 295 and 654 days post‐endoscopy. The remaining 17 cats did not show clinical signs of CE after a median of 709 days (range, 219‐869 days).

Conclusions and Clinical Importance

Intestinal biopsy specimens from clinically healthy client‐owned cats commonly had abnormal findings on histopathology, immunohistochemistry, clonality testing, or some combination of these without apparent clinical relevance. Current diagnostic metrics for diagnosing CE in cats may need modification to be applicable to the general population of cats.

A review of canine B cell clonality assays and primer set optimization using large-scale repertoire data

Several molecular clonality assays have been developed to assess canine B cell proliferations. These assays were based on different sequence data, utilized different assay designs and employed different testing strategies. This has resulted in a complex body of literature and complicates evidence-based selection of primer sets. In addition, further refinement of primer sets is difficult because it is unknown how well current primer sets cover the expressed sequence repertoire. The objectives of this study were 1) to provide an overview of published IGH clonality assays that highlights key differences in assay design and testing strategy and 2) to propose a novel method for optimizing primer sets that leverages large-scale sequencing data. A review of previously published assays highlighted confounding factors that hamper a direct comparison of performance metrics between studies. These findings illustrate the need for a multi-institutional effort to harmonize veterinary clonality testing. A novel in silico analysis of primer sequences using a large dataset of expressed sequences identified shortfalls of existing primer sets and was used to guide primer optimization. Three optimized primer sets were tested and yielded qualitative sensitivity values between 80-90%. The qualitative sensitivity ranged from 1% to over 50% and was dependent on the size of the neoplastic clone and the sample DNA used. These findings illustrate that inclusion of high-throughput sequencing data for primer design can be a useful tool to guide primer design and optimization. This strategy could be applied to other antigen receptor loci or species to further improve veterinary clonality assays.

Monitoring minimal residual disease in canine lymphomas treated with modified L-COP or L-CHOP protocols

Heteroduplex polymerase chain reaction for antigen receptor rearrangements (hPARR) was developed to monitor minimal residual disease (MRD) in canine B- and T-cell lymphomas treated with the modified L-COP or L-CHOP protocol. Thirty-five dogs were recruited in this study and their neoplastic lineages were determined by immunophenotyping with Pax5 and CD3. Peripheral blood leukocytes were collected prior to and during chemotherapy in weeks 4, 9 and 13 to detect MRD by hPARR. Twenty-eight dogs (80%) had B-cell lymphoma while seven dogs (20%) had T-cell lymphoma. A monoclonal band was detected in 11 cases that showed complete or partial remission before tumour relapse and no response to the current treatment without statistical difference in clinical outcomes; however, the treatment response had an association with the MRD result (P < 0.05). Modified L-CHOP prolonged median progression-free survival as compared to modified L-COP (215 days vs. 93 days; P < 0.05). Substage b had shorter progression-free survival than substage a (90 days vs. 215 days; P < 0.05). Clinical stage III affected median overall survival time when compared to clinical stages IV and V (432, 173 and 118 days, respectively; P < 0.05). hPARR could be used for screening refractory lymphoma together with lymph node measurement in routine clinical cases.

Corrigendum: Dogs with Acute Myeloid Leukemia Have Clonal Re-arrangements in T and B Cell Receptors

[This corrects the article on p. 76 in vol. 4, PMID: 28620611.].

Diagnosis of Lymphoid Malignancy by PCR for Analysis of Antigen Receptor Rearrangement after Blood Transfusion in a Dog with Acute Lymphocytic Leukemia

Acute lymphocytic leukemia (ALL) is uncommon lymphoid malignancy in dogs, and its diagnosis is challenging. A 14-year-old spayed female mixed breed dog was transferred to a veterinary medical teaching hospital for an immediate blood transfusion. The dog showed lethargy, pale mucous membranes, and a weak femoral pulse. Complete blood count revealed non-regenerative anemia and severe leukopenia with thrombocytopenia. ALL was tentatively diagnosed based on the predominance of immature lymphoblasts on blood film examination. For confirmation of lymphoid malignancy, PCR for antigen receptor rearrangement (PARR) on a peripheral blood sample and flow cytometry analysis were performed after blood transfusion. Flow cytometry analysis revealed that lymphocyte subsets were of normal composition, but PARR detected a T-cell malignancy. The dog was diagnosed with ALL and survived 1 wk after diagnosis. In conclusion, after blood transfusion, flow cytometry was not a reliable diagnostic method for an ALL dog, whereas PARR could detect lymphoid malignancy. Our results suggest that PARR should be the first-line diagnostic tool to detect canine lymphoid malignancy after a blood transfusion.

Optimisation and validation of a PCR for antigen receptor rearrangement (PARR) assay to detect clonality in canine lymphoid malignancies

•

Ten primer sets detected clonality with high specificity and sensitivity.

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Four extra primer sets may detect clonality in samples with equivocal results.

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Knowledge of sample quality is needed for interpretation of results.

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Samples generating dominant peaks require careful interpretation.

PCR for antigen receptor gene rearrangements (PARR) analysis is being increasingly used to assist diagnosis of canine lymphoma. In this study, PARR was carried out on consecutive samples received as part of routine diagnostic practice from 271 patients: 195 with lymphoid malignancies, 53 with reactive conditions and 23 with other neoplasms. Initially, published primer sets were used but later minor primer modifications were introduced and primers were rationalised to give a PARR panel that provides a good compromise between sensitivity and cost. Results were compared to diagnoses made by histology or cytology, coupled with immunophenotyping by flow cytometry or immunohistochemistry where possible. After exclusion of 11 poor quality samples, 230/260 (88%) gave a clear result with 162/163 (99%) of samples classified as clonal and 56/67 (84%) classified as polyclonal giving results concordant with the cytological/histological diagnosis. Among 30 samples with equivocal results, 21 had clonal peaks in a polyclonal background and nine showed little amplification. These were from patients with a range of neoplastic and non-neoplastic conditions emphasising the need to interpret such results carefully in concert with other diagnostic tests. The combination of primer sets used in this study resulted in a robust, highly specific and sensitive assay for detecting clonality.

Composition of lymphocyte subpopulations in normal canine lymph nodes

BACKGROUND

Flow cytometric immunophenotyping of lymph node aspirates has become a standard practice of canine lymphoma diagnostic workup. Ultimately, the combination of flow cytometry data, histopathology, and clinical signs allows consensus classification, and improves prognostic accuracy and therapeutic approaches.

OBJECTIVES

Although there is a growing body of information regarding lymphocyte population subsets in various types of lymphoma, only few studies provide information regarding the composition of the normal canine lymph node. The aim of this prospective study was to establish exploratory reference data for lymphocyte subpopulations in normal canine lymph nodes using an extended panel of antibodies.

METHODS

Popliteal lymph nodes excised from normal dogs were analyzed by cytology, multi-color flow cytometry using 11 different canine-specific and anti-human cross-reactive monoclonal antibodies, and polymerase chain reaction for antigen receptor rearrangement (PARR).

RESULTS

Subpopulations from lymph nodes of 26 dogs were classified according to the following positive antibody reactions: CD11a(+) 92.2 ± 12.3%, CD3(+) 55.0 ± 14.1%, CD3-12(+) 57.3 ± 14%, CD5(+) 52.3 ± 12.7%, CD21(+) 33.9 ± 11.8%, CD79αcγ(+) 46.9 ± 14.8%, CD56(+) 4.9 ± 5.9%, and CD14(+) 5.5 ± 6.8%. There were 58.7 ± 9% CD4(+) and 21.3 ± 7.8% CD8(+) cells inside the gate of CD3(+) cells. Cytology revealed a mixed population of mostly lymphoid cells in all samples. The absence of a monoclonal or oligoclonal neoplastic population was confirmed by PARR.

CONCLUSION

This study establishes for the first time flow cytometry data of lymphocyte populations in a larger group of normal canine lymph nodes, including populations positive for some new antibodies against CD3-12, CD5, CD11a, CD56, and CD79αcy.