Serum proteome profiles in cats with chronic enteropathies.

BACKGROUND: Serum protein biomarkers are used to diagnose, monitor treatment response, and to differentiate various forms of chronic enteropathies (CE) in humans. The utility of liquid biopsy proteomic approaches has not been examined in cats. HYPOTHESIS/OBJECTIVES: To explore the serum proteome in cats to identify markers differentiating healthy cats from cats with CE. ANIMALS: Ten cats with CE with signs of gastrointestinal disease of at least 3 weeks duration, and biopsy-confirmed diagnoses, with or without treatment and 19 healthy cats were included. METHODS: Cross-sectional, multicenter, exploratory study with cases recruited from 3 veterinary hospitals between May 2019 and November 2020. Serum samples were analyzed and evaluated using mass spectrometry-based proteomic techniques. RESULTS: Twenty-six proteins were significantly (P < .02, ≥5-fold change in abundance) differentially expressed between cats with CE and controls. Thrombospondin-1 (THBS1) was identified with >50-fold increase in abundance in cats with CE (P < 0.001) compared to healthy cats. CONCLUSIONS AND CLINICAL IMPORTANCE: Damage to the gut lining released marker proteins of chronic inflammation that were detectable in serum samples of cats. This early-stage exploratory study strongly supports THBS1 as a candidate biomarker for chronic inflammatory enteropathy in cats.

Serum proteome of dogs with chronic enteropathy.

BACKGROUND: Chronic enteropathy (CE) is common in dogs and can occur with multiple etiologies including food-responsive enteropathy (FRE) and idiopathic inflammatory bowel disease (IBD). HYPOTHESIS/OBJECTIVE: To study the protein profile and pathway differences among dogs with FRE, IBD, and healthy controls using serum proteome analysis. ANIMALS: Nine CE dogs with signs of gastrointestinal disease and histologically confirmed chronic inflammatory enteropathy and 16 healthy controls. METHODS: A cross-sectional study with cases recruited from 2 veterinary hospitals between May 2019 and November 2020 was performed. Serum samples were analyzed using mass spectrometry-based proteomic techniques. RESULTS: Proteomic profiles showed marked variation in relative protein abundances. Forty-five proteins were significantly (P ≤ .01) differentially expressed among the dogs with CE and controls with ≥2-fold change in abundance. The fold change of dogs with IBD normalized to controls was more pronounced for the majority of proteins than that seen in the dogs with FRE normalized to control dogs. Proteins involving reactive oxygen species, cytokine activation, acute phase response signaling, and lipid metabolism were altered in dogs with CE. CONCLUSIONS AND CLINICAL IMPORTANCE: Cytokine alterations, acute phase response signaling, and lipid metabolism are likely involved in pathogenesis of CE. Although there are insufficient current data to justify the use of proteomic biomarkers for assessment of CE in dogs, our study identifies potential candidates.

Giardia duodenalis in a clinically healthy population of captive zoo chimpanzees: Rapid antigen testing, diagnostic real-time PCR and faecal microbiota profiling.

Giardia duodenalis is one of the most common intestinal parasites of humans, with a worldwide distribution. Giardia duodenalis has been reported in both wild and captive populations of non-human primates, namely chimpanzees. In this study we investigated an entire troop of clinically healthy chimpanzees (n = 21) for the presence of G. duodenalis and its association with faecal microbiota profile. Faecal samples (n = 26) were collected from the chimpanzee exhibit from a zoo in Sydney, Australia. Diagnosis of G. duodenalis was made using a Rapid Antigen Test (RAT) as a point-of-care-test and compared to a reference standard real-time PCR test. Approximately half of the chimpanzee faecal samples tested positive for G. duodenalis by both RAT (13/26, 50%) and real-time PCR (14/26, 53.85%). The RAT sensitivity was 85.7% (95% CI: 63.8%-96%) and specificity was 91.7% (95% CI: 68.3%-99%) when compared to the in-house real-time PCR. Genotyping of the samples revealed the presence of zoonotic assemblage B. Microscopic analysis revealed the presence of Troglodytella spp. (14/26), Balantioides sp. (syn. Balantidium sp.) (8/26) as well as Entamoeba spp. (3/26). Microbiota profile based on 16S rRNA gene sequencing revealed that the community was significantly different between G. duodenalis positive and negative samples if RAT results were taken into an account, but not real-time PCR diagnostics results. Proteobacteria and Chloroflexi were the significant features in the dataset that separated G. duodenalis positive and negative samples using LEfSe analysis. Being able to rapidly test for G. duodenalis in captive populations of primates assists in point-of-care diagnostics and may better identify animals with subclinical disease. Under the investigated conditions of the zoo setting, however, presence of G. duodenalis either detected by RAT or real-time PCR was not associated with clinically apparent disease in captive chimpanzees.

Videofluoroscopy, CT angiography, and ultrasonography of congenital esophageal stenosis in a Labrador retriever.

A 7-week-old Labrador retriever presented for further investigation into acute onset regurgitation, following weaning from liquid to solid food. A videofluoroscopic swallow study demonstrated a severe, focal esophageal dilation in the mid-cervical region, with marked luminal narrowing distally. Computed tomography with angiography revealed esophageal stenosis, extending from C4-T2, secondary to circumferential esophageal wall thickening. With the concern for development of secondary aspiration pneumonia, the owners elected to euthanize the dog and consented to postmortem examination. A diagnosis of segmental, cervical esophageal muscular hypertrophy was made on necropsy, consistent with the fibromuscular thickening type of congenital esophageal stenosis reported in humans.

Clinical relevance of splenic nodules or heterogeneous splenic parenchyma assessed by cytologic evaluation of fine-needle samples in 125 dogs (2011-2015).

BACKGROUND: Splenic nodules and heterogeneous parenchyma are seen frequently in abdominal ultrasound examinations of dogs, but the clinical importance of these lesions remains unclear. OBJECTIVES: To determine whether specific ultrasonographic findings correlate with clinically relevant cytologic diagnoses and determine what sonographic features are correlated with these diagnoses. Another objective was to develop a scoring rubric to help clinicians make decisions on whether or not certain ultasonographic findings of the spleen warrant evaluation by fine-needle cytology. ANIMALS: One-hundred twenty-five adult client-owned dogs with ultrasonographically identified splenic nodules, heterogeneous parenchyma, or both. METHODS: Medical records were retrospectively searched for ultrasound-guided splenic fine-needle cytology reports. Ultrasonographic images were assessed for nodule number, size, echogenicity and distal enhancement, degree of splenic heterogeneity, and peritoneal fluid. Dogs were divided into 2 groups: those with clinically important or clinically irrelevant cytologic findings. Potentially useful and discriminatory ultrasonographic findings were identified by statistical analysis, and the most useful findings were used to generate the scoring rubric. RESULTS: The clinically important group included 25 of 125 dogs (22 malignancies, 3 suppurative inflammation). Splenic nodules 1-2 cm in diameter, peritoneal fluid, and >1 targetoid nodule were associated with clinically important cytologic findings. Receiver operator characteristic analysis showed that the scoring rubric was useful for identifying dogs in the clinically important group. CONCLUSIONS AND CLINICAL IMPORTANCE: Splenic fine-needle cytologic findings identified a clinically relevant diagnosis in 20% of dogs, and larger nodule size, number of targetoid lesions, and presence of peritoneal fluid increase the likelihood of detection of clinically important disease.

Immediate effect of transmucosal application of corn syrup or 50% dextrose solution on blood glucose concentrations in healthy dogs.

OBJECTIVE: Evaluate and quantify the effects of mucosal corn syrup and 50% dextrose application on blood glucose concentrations in healthy dogs, to assess the effectiveness of a widely used practice for treatment of hypoglycemia. DESIGN: Randomized controlled trial. SETTING: University teaching hospital. ANIMALS: Twelve client-owned dogs that were healthy, >1 year of age, weighing >5 kg, and had normal physical exam and biochemical profiles. INTERVENTIONS: Dogs were fasted overnight for a minimum of 12 hours. Once normal physical exam and biochemical profile were confirmed, an IV catheter was placed in a peripheral vein for serial blood sampling. Each dog served as their own control and received each of 3 treatments, the orders of which were randomized for each dog. Treatments included mucosal application of commercially available corn syrup (Karo light syrup), water (control), and 50% dextrose solution, each at a dose of 1 mL/kg of body weight. Blood glucose was measured using a point-of-care glucometer. Samples were taken immediately prior to each treatment and at 5-, 10-, 15-, 20-, 30-, and 60-minute intervals. RESULTS: All treatments were well tolerated and no adverse events were observed. A statistically significant increase in blood glucose was observed at the 15-, 20-, 30-, and 60-minute time points in the corn syrup and 50% dextrose groups as compared with the control. CONCLUSIONS: A significant effect on the blood glucose concentrations of the treated animals was not observed until 15 minutes after application of concentrated glucose solutions. These findings suggest that, in more severely hypoglycemic patients, parenteral glucose administration may be necessary.

Obstructive sleep apnea in a Chihuahua successfully managed with ondansetron.

While the persistence of clinical signs related to brachycephalic obstructive airway syndrome, particularly sleep-disordered breathing patterns following appropriate surgical management is likely to be relatively rare, this potential sequela needs to be considered, along with being aware of possible medical management options such as serotonin antagonists.

Presumed immune-mediated haemolytic anaemia associated with pregnancy in a cat.

CASE SUMMARY: A 7-year-old female entire Birman presented with acute-onset haemorrhagic vulvar discharge. Moderate, normocytic, normochromic, non-/pre-regenerative anaemia, along with a moderate mature neutrophilia, were seen on haematology. Saline test for agglutination was positive. No haemotropic mycoplasmas were identified. Serum biochemistry revealed severe hyperbilirubinaemia. Retroviral testing was negative. Serology for toxoplasmosis revealed a titre of 1:512. Abdominal ultrasound identified a large uterus, containing at least three advanced-stage fetuses, two of which failed to exhibit independent motion or cardiac activity. Ovariohysterectomy was performed. Histology demonstrated mild, multifocal suppurative placentitis, with Gram staining revealing no evidence of bacteria. Complete resolution of the anaemia was seen within 1.5 months of ovariohysterectomy. RELEVANCE AND NOVEL INFORMATION: Immune-mediated haemolytic anaemia (IMHA) in association with pregnancy has not been previously reported in cats. This case represents a potential novel cause for IMHA in cats, which resolved following ovariohysterectomy.

Clinical evaluation of a benchtop dry chemistry analyzer for measurement of ammonium concentrations in canine plasma samples.

OBJECTIVE To evaluate the clinical performance of a veterinary benchtop dry chemistry analyzer for measurement of plasma ammonium concentrations in dogs by comparing results with those obtained by a reference standard test method. DESIGN Prospective evaluation study. SAMPLE 32 blood samples from 30 dogs (16 with and 14 without suspected hepatobiliary disease). PROCEDURES Blood samples were collected by jugular venipuncture. A veterinary benchtop dry chemistry analyzer and a reference standard (enzymatic) test method were used to measure ammonium concentrations in plasma collected from heparinized whole blood. Bland-Altman plots were used to assess intermethod agreement. Results were compared by linear regression, and correlation was calculated by the Pearson method. Samples were classified as having high or normal ammonium concentrations on the basis of cutoff data for the relevant test method; results were compared between methods to evaluate diagnostic agreement. RESULTS 31 of 32 (97%) samples were classified correctly with the benchtop analyzer; 1 sample with a high ammonium concentration was classified as having a normal value (ie, false-negative result) by this method. A strong positive correlation (r2 = 0.989) was found between methods, with constant, proportional, negative bias for benchtop analyzer results. The interassay coefficient of variation (ie, precision) for measurement of an internal standard with the benchtop analyzer was 2.74% (n = 20 repetitions). CONCLUSIONS AND CLINICAL RELEVANCE The dry chemistry analyzer used in the study had acceptable clinical performance for detection of high versus normal ammonium concentrations in canine plasma, indicating the method can be used to aid diagnosis in dogs with suspected hepatobiliary disease.

Evaluation of the clinical effects of diet and physical rehabilitation in dogs following tibial plateau leveling osteotomy.

OBJECTIVE To assess clinical effects of an omega-3 fatty acid and protein-enriched diet, physical rehabilitation, or both in dogs following tibial plateau leveling osteotomy (TPLO) and arthroscopic surgery for cranial cruciate ligament (CCL) disease. DESIGN Randomized, prospective clinical trial. ANIMALS 48 dogs with unilateral CCL disease. PROCEDURES Dogs were randomly assigned to receive a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health (test food [TF]), a dry food formulated for maintenance of adult dogs (control food [CF]), TF plus rehabilitation (TF-R), or CF plus rehabilitation (CF-R). Data collected over 6 months included body weight, body condition score, ground reaction force data, tibial plateau angle, limb circumference measurements, subjective pain and lameness scores assigned by surgeons and dog owners, and daily activity measured by accelerometry. RESULTS Peak vertical force and vertical impulse were greater after surgery for dogs in the TF groups than in the CF groups; peak vertical force was greater after surgery in dogs that underwent rehabilitation than in those that did not. Owner scores indicated lower frequencies of lameness and signs of pain during some activities for the TF group, compared with other groups, and for the TF-R and CF-R groups, compared with the CF group. Sedentary time decreased and time spent in light-to-moderate or vigorous activity increased in all groups over time. Rehabilitation was significantly associated with greater time spent in light-to-moderate activity, regardless of diet. CONCLUSIONS AND CLINICAL RELEVANCE Feeding the TF and providing physical rehabilitation during the first 6 months after TPLO were associated with improvements in some indices of clinical outcome and function in dogs. Significant interactions between time and some outcome variables were observed, indicating further research is warranted.

Assessment of the effects of diet and physical rehabilitation on radiographic findings and markers of synovial inflammation in dogs following tibial plateau leveling osteotomy.

OBJECTIVE To determine the effects of an omega-3 fatty acid and protein-enriched diet, physical rehabilitation, or both on radiographic findings and markers of synovial inflammation in dogs following tibial plateau leveling osteotomy and arthroscopic surgery for treatment of cranial cruciate ligament disease. DESIGN Randomized, prospective clinical trial. ANIMALS 48 dogs with unilateral cranial cruciate ligament disease. PROCEDURES Dogs were randomly assigned to receive a dry omega-3 fatty acid and protein-enriched dog food formulated to support joint health (test food [TF]), a dry food formulated for adult canine maintenance (control food [CF]), TF plus rehabilitation, or CF plus rehabilitation after surgery. Synovial fluid prostaglandin (PG) E2 and interleukin-1ß concentrations, radiographic osteoarthritis scores, osteotomy site healing, and patellar ligament thickness were assessed at predetermined time points up to 6 months after surgery. RESULTS Dogs that received CF had significantly higher PGE2 concentrations over time following surgery than did dogs that received TF, regardless of rehabilitation status. Synovial fluid interleukin-1ß concentrations did not change over time in any groups. Diet and rehabilitation were both associated with osteoarthritis scores, with significantly lower scores over time for dogs that received TF versus CF and for dogs that underwent rehabilitation versus those that did not. Proportions of dogs with complete osteotomy healing 8 and 24 weeks after surgery were significantly lower for dogs that received TF than for dogs that received CF, regardless of rehabilitation status. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that feeding the TF can result in lower synovial fluid PGE2 concentrations and that both the TF and rehabilitation can reduce progression of osteoarthritis in the 6 months following tibial plateau leveling osteotomy; clinical relevance of slower osteotomy healing in dogs fed the TF was unclear.

Estimates of biologic variation in specific feline pancreatic lipase concentrations in cats without clinical or ultrasonographic evidence of pancreatitis.

BACKGROUND: Serum concentrations of feline-specific pancreatic lipase are commonly used for diagnosis and monitoring of pancreatitis in cats, but little is known regarding biologic variation of this analyte. OBJECTIVES: The purpose of the study was to determine biologic variation, index of individuality, and reference change values (RCV) for specific feline pancreatic lipase concentrations (Spec fPL) in apparently healthy cats. METHODS: Four blood samples were collected prospectively from 12 apparently healthy cats at 2-week intervals. The Spec fPL was measured in all serum samples by a reference laboratory. RESULTS: Intra-individual variation for Spec fPL was 33.5% (95% CI 27.1-43.8%); inter-individual variation was 99.9% (69.2-169.9%) and analytic variation was 7.3% (6.1-9.2%). Reciprocal index of individuality for Spec fPL was 2.9 (2.5-3.8), the 2-sided RCV was 95.1% (77.0-123.9%). CONCLUSIONS: Due to high individuality, use of a population-based RI for Spec fPL may fail to detect clinically significant elevations in individual cats. The use of subject-based RIs for Spec fPL may have greater sensitivity for the detection of a change in pancreatic physiology in cats; however, this would require serial assessment of apparently healthy cats.

Family Dog-Assisted Adapted Physical Activity: A Case Study.

Purpose: The aim of this case study was to examine the individual effects of an adapted physical activity, animal-assisted intervention (APA-AAI) with the family dog on motor skills, physical activity, and quality of life of a child with cerebral palsy (CP). Method: This study used an A-B-A single-subject design. The assessment phase (phase A) occurred pre- and post-intervention. This consisted of standardized assessments of motor skills, quality of life questionnaires, physical activity (measured using the GT3X+ accelerometer) and the human-animal bond. The intervention (phase B) lasted 8 weeks and consisted of adapted physical activities performed with the family dog once a week for 60 min in a lab setting. In addition, the participant had at-home daily activities to complete with the family dog. Results: Visual analysis was used to analyze the data. Motor skill performance, physical activity, quality of life and human animal interaction gains were observed in each case. Conclusions: These preliminary results provided initial evidence that the family-dog can play a role in healthy lifestyles through APA-AAI in children with CP.

Expression of serotonin, chromogranin-A, serotonin receptor-2B, tryptophan hydroxylase-1, and serotonin reuptake transporter in the intestine of dogs with chronic enteropathy.

Serotonin regulates many intestinal motor and sensory functions. Altered serotonergic metabolism has been described in human gastrointestinal diseases. The objective of our study was to compare expression of several components of the serotonergic system [serotonin (5-HT), serotonin reuptake transporter protein (SERT), tryptophan hydroxylase-1 (TPH-1), 5-HT receptor2B (5-HT2B)] and the enterochromaffin cell marker chromogranin-A (CgA) in the intestinal mucosa between dogs with chronic enteropathy and healthy controls. Serotonin and CgA expression were determined by immunohistochemistry using banked and prospectively obtained, paraffin-embedded canine gastrointestinal biopsies (n = 11), and compared to a control group of canine small intestinal sections (n = 10). Expression of SERT, TPH-1, and 5-HT2B were determined via real-time reverse transcription (qRT)-PCR using prospectively collected endoscopic duodenal biopsies (n = 10) and compared to an additional control group of control duodenal biopsies (n = 8, control group 2) showing no evidence of intestinal inflammation. Dogs with chronic enteropathies showed strong staining for both 5-HT and CgA. Mean positive cells per high power field (HPF) were significantly increased for both compounds in dogs with chronic enteropathies (p < 0.001 for 5-HT; p < 0.05 for CgA). The number of 5-HT-positive and CgA-positive cells/HPF showed significant correlation in the entire group of dogs, including both diseased and healthy individuals (Pearson r(2) = 0.2433, p = 0.016). No significant differences were observed for SERT, TPH-1, or 5-HT2B expression; however, dogs with chronic enteropathy showed greater variability in expression of TPH-1 and 5-HT2B We conclude that components of the neuroendocrine system show altered expression in the intestinal mucosa of dogs with chronic enteropathy. These changes may contribute to nociception and clinical signs in these patients.

Validation of an enzyme-linked immunosorbent assay (ELISA) for the measurement of canine S100A12.

BACKGROUND: Canine S100 calcium-binding protein A12 (cS100A12) shows promise as biomarker of inflammation in dogs. A previously developed cS100A12-radioimmunoassay (RIA) requires radioactive tracers and is not sensitive enough for fecal cS100A12 concentrations in 79% of tested healthy dogs. An ELISA assay may be more sensitive than RIA and does not require radioactive tracers. OBJECTIVE: The purpose of the study was to establish a sandwich ELISA for serum and fecal cS100A12, and to establish reference intervals (RI) for normal healthy canine serum and feces. METHODS: Polyclonal rabbit anti-cS100A12 antibodies were generated and tested by Western blotting and immunohistochemistry. A sandwich ELISA was developed and validated, including accuracy and precision, and agreement with cS100A12-RIA. The RI, stability, and biologic variation in fecal cS100A12, and the effect of corticosteroids on serum cS100A12 were evaluated. RESULTS: Lower detection limits were 5 µg/L (serum) and 1 ng/g (fecal), respectively. Intra- and inter-assay coefficients of variation were ≤ 4.4% and ≤ 10.9%, respectively. Observed-to-expected ratios for linearity and spiking recovery were 98.2 ± 9.8% (mean ± SD) and 93.0 ± 6.1%, respectively. There was a significant bias between the ELISA and the RIA. The RI was 49-320 µg/L for serum and 2-484 ng/g for fecal cS100A12. Fecal cS100A12 was stable for 7 days at 23, 4, -20, and -80°C; biologic variation was negligible but variation within one fecal sample was significant. Corticosteroid treatment had no clinically significant effect on serum cS100A12 concentrations. CONCLUSIONS: The cS100A12-ELISA is a precise and accurate assay for serum and fecal cS100A12 in dogs.

Biologic variability in NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral valve degeneration.

BACKGROUND: The N-terminal fragment of the prohormone B-type natriuretic peptide (NT-proBNP) and cardiac troponin-I are candidate biomarkers for cardiac disease in dogs. The degree of biologic variation in these biomarkers has not previously been reported in healthy dogs or dogs with mitral regurgitation. OBJECTIVES: The purpose of the study was to derive estimates of intrinsic biologic variability and reference change values for NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral regurgitation grade IB and II according to the International Small Animal Cardiac Health Council (ISACHC) grading system. METHODS: Plasma and sera were collected weekly for up to 7 weeks from 12 control dogs and 9 dogs with mitral regurgitation. NT-proBNP and troponin-I (C-TnI) concentrations were determined. Indices of biologic variation such as reciprocal index of individuality (r-IoI) and reference change values (RCV) were calculated in both the groups. RESULTS: Individuality was high in control dogs and dogs with grade IB and II mitral valve regurgitation for both C-TnI (r-IoI 1.6 and 2) and NT-proBNP (1.5 and 2.7), while the 2-sided RCV for NT-proBNP was significantly lower in dogs with mitral regurgitation (52.5% vs 99.4%, P<0.01.). CONCLUSIONS: High individuality of these cardiac biomarkers suggests that, following diagnosis, these assays are best interpreted by serial determination in individual canine patients rather than by comparison to a population-based reference interval. The smaller RCV values for dogs with mitral regurgitation suggest that smaller relative changes in NT-proBNP are clinically meaningful in these patients.

Characterization, treatment, and outcome of bacterial cholecystitis and bactibilia in dogs.

Objective-To characterize historical, clinicopathologic, ultrasonographic, microbiological, surgical, and histopathologic features of bacterial cholecystitis and bactibilia in dogs and evaluate response to treatment and outcomes in these patients. Design-Retrospective case-control study. Animals-40 client-owned dogs (10 with bacterial cholecystitis on histologic analysis or bactibilia on cytologic examination [case dogs] and 30 without bactibilia [controls]) evaluated at a veterinary teaching hospital between 2010 and 2014. Procedures-Signalment, history, clinicopathologic findings, ultrasonographic features, microbiological results, surgical findings, histopathologic changes, treatments, and outcomes of case dogs were derived from medical records and summarized. Demographic and clinicopathologic data and ultrasonographic findings were compared between case and control dogs. Relationships among prior antimicrobial treatment, sediment formation in the gallbladder, presence of immobile biliary sludge, and presence of bactibilia or bacterial cholecystitis were assessed. Results-No finding was pathognomonic for bactibilia or bacterial cholecystitis in dogs. Case dogs were significantly more likely to have immobile biliary sludge and had a greater degree of biliary sediment formation than did control dogs. All case dogs for which gallbladders were examined histologically (6/6) had bacterial cholecystitis. Five of 10 case dogs were Dachshunds. Medical or surgical treatment resulted in good outcomes. Conclusions and Clinical Relevance-Bactibilia and bacterial cholecystitis were important differential diagnoses in dogs with signs referable to biliary tract disease. Dachshunds were overrepresented, which may suggest a breed predisposition. Cytologic evaluation of bile should be considered in the routine assessment of dogs with hepatobiliary disease if immobile biliary sludge is present. (J Am Vet Med Assoc 2015;246:982-989).

Biphenotypic B-cell lymphoma in 2 cats.

The clinical and pathologic features of biphenotypic B-cell lymphoma in 2 cats are reported. Clinical presentation varied from multiple cutaneous masses identified on the thigh in one cat to signs of lethargy from acute hemorrhage due to neoplastic infiltration of one kidney in the other. Cytology and histopathology confirmed round cell neoplasia in both cats and immunochemical staining demonstrated expression of both B- and T-lymphocyte markers by the neoplastic cells in both animals. In PCR analysis of antigen receptor gene rearrangement, clonal rearrangement of B-cell receptor genes and polyclonal T-cell receptor gene rearrangement were demonstrated in both lymphomas. These findings were consistent with a diagnosis of B-cell lymphoma with aberrant CD3 expression in both cases. Clinical progression of disease post diagnosis was rapid in both cats, suggesting a poor prognosis for this lymphoma type. Although bigenotypic receptor rearrangement of lymphoma cells appears relatively common, this is the first known report of actual biphenotypic lymphoma in cats.