Evaluation of PEG-L-asparaginase in asparagine suppression and anti-drug antibody development in healthy Beagle dogs: A multi-phase preclinical study.

L-asparaginase is a frequently used drug in the treatment of canine malignant lymphoma. Since production and availability of native E. coli-derived L-asparaginase are limited, PEG-L-asparaginase (PEG-ASP) is an alternative. However, recommended doses and dosing intervals are mainly empirically determined. A multi-phase clinical dose-finding study with seven healthy Beagle dogs was conducted to find the minimum effective dose and, potentially, a dosing interval for PEG-ASP in dogs. Plasma concentrations of amino acids and PEG-ASP activity were measured at various time points after administration of different doses of PEG-ASP. Anti-PEG and anti-asparaginase antibody titres were measured. Administration of 10 IU/kg PEG-ASP resulted in asparagine depletion in all dogs, albeit for various durations: for 9 days in all dogs, 15 days in five dogs, 21 days in three dogs and 29 days in one dog. Asparagine suppression occurred at PEG-ASP plasma concentrations < 25 IU/L. Subsequent administrations of a second and third dose of 20 IU/kg and 40 IU/kg PEG-ASP resulted in asparagine suppression at < 9 days in five dogs, accompanied by the development of antibodies against PEG and L-asparaginase. Two dogs with prolonged asparagine suppression after the second and third administration did not develop antibodies. Marked individual variation in the mechanism and duration of response to PEG-ASP was noted. Antibody formation against PEG-ASP was frequently observed and sometimes occurred after one injection. This study suggests that PEG-ASP doses as high as the currently used dose of 40 IU/kg might not be needed in treatment of canine malignant lymphoma.

Evaluation of urinary and serum level of chemokine (C-C motif) ligand 2 as a potential biomarker in canine urothelial tumours.

Chemokine (C-C motif) ligand 2 (CCL2) is a chemotactic cytokine recruiting monocytes, releasing growth factors and promoting adhesion in vascular endothelium. Elevated serum and urinary CCL2 levels and expression of its receptor (CCR2) have been associated with tumorigenesis in human urinary malignancies. CCL2 implication has not been investigated in canine urothelial carcinoma. The aim of this study was to evaluate CCL2 serum and urine levels (measured by ELISA) in dogs with urothelial carcinoma or non-neoplastic urinary tract disease. CCL2 serum and urine levels were significantly higher in diseased dogs compared with healthy dogs (P < 0.001). Dogs with carcinoma had significantly higher serum and urine CCL2 levels (P = 0.001) than healthy dogs. Dogs with metastases showed significantly lower serum and urine CCL2 levels compared with the non-metastasised tumour group (P = 0.007). CCL2 as a diagnostic marker for urothelial carcinoma held a sensitivity of 95.2% and a specificity of 38.2% in the urine. As a staging marker, sensitivity was 85.7% and specificity was 57.1% with a positive predictive value of 75.7% and a negative predictive value of 71.9%. Further investigation is needed to define the role of CCL2 as a prognostic marker in canine urothelial carcinoma.

Compartmental resection of peripheral nerve tumours with limb preservation in 16 dogs (1995-2011).

Peripheral nerve tumours (PNTs) affecting the limbs may lead to chronic pain, lameness and/or monoparesis that is refractory to medical treatment. The most common radical therapy for PNTs has been surgical excision with limb amputation. However, compartmental resection with preservation of the limb has been performed by the authors with favourable clinical results and therefore this bi-institutional retrospective study was undertaken to assess limb function, survival and recurrence. Sixteen dogs that had been diagnosed with PNTs between 1995 and 2011 met the inclusion criteria for this study. In the majority of the cases, good to excellent limb function was achieved. The overall median survival time (MST) was 1303days (42.8 months; range, 14 days-4639 days, [0.5-152.4 months]), with two dogs still alive at time of evaluation. Non-infiltrated margins were the best prognostic indicator; dogs with non-infiltrated margins had a MST of 2227days (P<0.001) compared to dogs with infiltrated margins (MST of 487 days). The 1-year calculated survival rate was 68.8% and the 2- and 3-year calculated survival rates were 62.5%. Surgical treatment with tumour removal and limb spare for proximal and distal PNTs can be successful. Compartmental excision can lead to good limb function, producing survival comparable to limb amputation, and should therefore be considered as an alternative to limb amputation in canine PNTs.

Effects of clopidogrel therapy on whole blood platelet aggregation, the Plateletworks® assay and coagulation parameters in cats with asymptomatic hypertrophic cardiomyopathy: a pilot study.

BACKGROUND: Although scientific evidence is limited, clopidogrel is frequently used as prophylaxis for arterial thromboembolism in cats with hypertrophic cardiomyopathy (HCM). OBJECTIVES: Evaluating effects of clopidogrel therapy in asymptomatic cats with HCM on (1) conventional whole blood aggregation (WBA), (2) alternative platelet aggregation assessed with tubes of the Plateletworks® assay and (3) standard coagulation parameters. ANIMALS AND METHODS: Prospective, randomized, double-blind, placebo-controlled pilot study. Fourteen asymptomatic HCM cats were randomly allocated to receive placebo (n = 5) or clopidogrel (18.75 mg/cat q24h, n = 9) as part of a larger study. Aggregation responses (to 20 µM adenosine diphosphate (ADP) and 10 µg/ml collagen) in WBA and the Plateletworks® assay and standard coagulation parameters were evaluated at baseline and after seven days of therapy. RESULTS: Clopidogrel therapy significantly reduced aggregation responses to ADP and collagen in the Plateletworks® agonists tubes (ADP and collagen: P < 0.001), but did not significantly reduce aggregation responses to ADP and collagen in the WBA technique (ADP: P = 0.07, collagen: P = 0.30). Clopidogrel therapy did not show a significant effect on prothrombin time, activated partial thromboplastin time, antithrombin, D-dimers and fibrinogen concentrations. CONCLUSION AND CLINICAL IMPORTANCE: Clopidogrel therapy at a dose of 18.75 mg/cat q24h for seven days causes a significant decrease in in vitro platelet aggregation evaluated with the Plateletworks® assay, without affecting standard coagulation parameters in cats with asymptomatic HCM.

Masitinib monotherapy in canine epitheliotropic lymphoma.

This study evaluated efficacy and side effects of masitinib in canine epitheliotropic lymphoma. Complete remission occurred in 2 of 10 dogs and lasted for median 85 days. Five dogs went into partial remission for median 60.5 days. Three pretreated dogs did not respond to therapy. Side effects occurred in six dogs and were mostly mild to moderate. Immunohistochemistry was available for eight dogs. KIT receptor was negative in all of them, six of eight lymphomas stained strongly positive for stem cell factor (SCF). platelet-derived growth factor (PDGF)-AA was weakly positive in two and negative in six. PDGF-BB was negative in four tumours, weakly positive in one and strongly positive in three. One was strongly positive for PDGF receptor (PDGFR)-ß, seven were negative for that receptor. Five showed strong expression of PDGFR-α, two showed weak expression, one was negative. In conclusion, masitinib is effective in treating canine epitheliotropic lymphoma. But its effects are most likely not generated through the KIT receptor.

Cytology of endoscopically obtained biopsies for the diagnosis of chronic intestinal diseases in cats.

OBJECTIVE: To evaluate the diagnostic value of cytology of endoscopically obtained biopsies in cats presented for chronic gastrointestinal complaints with emphasis on the diagnosis of low-grade alimentary lymphoma (LGAL). MATERIALS AND METHODS: Data of endoscopically obtained duodenal biopsies from 137 cats were evaluated retrospectively. Cytology was performed using the squash smear technique with subsequent Diff Quick® staining. Pathological findings were categorized according to type and grade of the inflammatory infiltrate. Moreover, reports were reviewed with regard to diagnosis of LGAL. Histopathology reports were analysed correspondingly and compared to cytology results. Histopathological samples were further evaluated by immunohistochemistry (IHC) if a diagnosis of LGAL had been expressed. RESULTS: Squash smear preparation of intestinal biopsies was adequate for cytological examination in >97% of cases. Using histopathology as gold standard, with cytology, a sensitivity and specificity for detection of a pathologic process in feline intestinal biopsies of 68.1% and 70.6% were calculated, respectively. Regarding the detection of lymphoplasmacytic (LPE) and eosinophilic enteritis a statistically significant correlation with histopathology (p<0.05) was observed. With regard to grade of the inflammatory infiltrate, a weak correlation was calculated (r=0.482). Of 21 cats diagnosed or suspected with LGAL by cytology, IHC confirmed nine cases whereas 11 cases were reclassified as LPE. None of the confirmed LGAL had been missed with histopathology. A sensitivity of 60.0% and specificity of 90.6% for cytological detection of feline LGAL was obtained. CONCLUSION AND CLINICAL RELEVANCE: The sensitivity of cytology to diagnose LGAL is low and it has no additional significance to histological biopsies.

Red blood cell phosphate concentration and osmotic resistance during dietary phosphate depletion in dairy cows.

BACKGROUND: Hypophosphatemia in early lactating dairy cows has been implicated as primary cause for postparturient hemoglobinuria in cattle. Decreased availability of phosphorus has been proposed to reduce adenosine triphosphate synthesis of erythrocytes and thereby reduce osmotic resistance of these cells. HYPOTHESIS/OBJECTIVES: To study the effect of phosphorus depletion on the phosphate concentration ([Pi]) in plasma and erythrocytes and the osmotic resistance of erythrocytes and to determine the association between plasma [Pi] and erythrocyte [Pi]. ANIMALS: Ten healthy midlactating dairy cows in their 3rd to 5th lactation. METHODS: Prospective study. Dietary phosphorus depletion for 5 weeks followed by phosphorus supplementation. Plasma and erythrocyte [Pi] and erythrocyte osmotic resistance were measured. Four cows underwent continuous dextrose infusion at the end of phosphate depletion to exacerbate hypophosphatemia. RESULTS: Dietary P depletion resulted in a marked decline of the plasma [Pi] from 4.1 ± 1.0 mg/dL to a nadir of 1.7 ± 0,5 mg/dL, but did not alter erythrocyte [Pi] or osmotic resistance. Similarly, dextrose infusion induced a decline of the plasma [Pi] from 2.4 ± 0.5 mg/dL to 1.5 ± 0.5 mg/dL, but had no effect on erythrocyte [Pi] or osmotic resistance. CONCLUSIONS AND CLINICAL IMPORTANCE: In cattle, marked hypophosphatemia induced by dietary P depletion was neither associated with a decline in erythrocyte [Pi] nor with decreased osmotic resistance of erythrocytes. Phosphorus depletion alone is therefore unlikely to cause intravascular hemolysis and the plasma [Pi] is an unreliable index for the intracellular [Pi] of erythrocytes.

A longitudinal study of ABC transporter expression in canine multicentric lymphoma.

Canine lymphoma is typically treated with a doxorubicin-based multidrug chemotherapy protocol. Although this is often initially successful, tumour recurrence is common and frequently refractory to treatment. Failure to respond to chemotherapy is thought to represent drug resistance and has been associated with active efflux of cytostatic drugs by transporter proteins of the ATP-binding cassette (ABC) family, including P-glycoprotein (ABCB1), MRP1 (ABCC1) and BCRP (ABCG2). In this study, ABC transporter mRNA expression was assessed in 63 dogs diagnosed with multicentric lymphoma that were treated with a doxorubicin-based chemotherapy protocol. Expression of ABCB1, ABCB5, ABCB8, ABCC1, ABCC3, ABCC5 and ABCG2 mRNA was quantified in tumour samples (n = 107) obtained at the time of diagnosis, at first tumour relapse and when the tumour was no longer responsive to cytostatic drugs while receiving chemotherapy. Expression data were related to patient demographics, staging, treatment response and drug resistance (absent, intrinsic, acquired). ABC transporter expression was independent of sex, weight, age, stage or substage, but T cell lymphoma and hypercalcaemia were associated with increased ABCB5 and ABCC5 expression, and decreased ABCC1 mRNA expression. Drug resistance occurred in 35/63 (55.6%) dogs and was associated with increased ABCB1 mRNA expression in a subset of dogs with B cell lymphoma, and with increased ABCG2 and decreased ABCB8, ABCC1 and ABCC3 mRNA expression in T cell lymphomas. ABC transporter expression in the pre-treatment sample was not predictive of the length of the first disease-free period or overall survival. Glucocorticoids had no effect on ABC transporter mRNA expression. In conclusion, drug resistance in canine multicentric lymphoma is an important cause of treatment failure and is associated with upregulation of ABCB1 and ABCG2 mRNA.

Multi-drug resistance in a canine lymphoid cell line due to increased P-glycoprotein expression, a potential model for drug-resistant canine lymphoma.

Canine lymphoma is routinely treated with a doxorubicin-based multidrug chemotherapy protocol, and although treatment is initially successful, tumor recurrence is common and associated with therapy resistance. Active efflux of chemotherapeutic agents by transporter proteins of the ATP-Binding Cassette superfamily forms an effective cellular defense mechanism and a high expression of these transporters is frequently observed in chemotherapy-resistant tumors in both humans and dogs. In this study we describe the ABC-transporter expression in a canine lymphoid cell line and a sub-cell line with acquired drug resistance following prolonged exposure to doxorubicin. This sub-cell line was more resistant to doxorubicin and vincristine, but not to prednisolone, and had a highly increased P-glycoprotein (P-gp/abcb1) expression and transport capacity for the P-gp model-substrate rhodamine123. Both resistance to doxorubicin and vincristine, and rhodamine123 transport capacity were fully reversed by the P-gp inhibitor PSC833. No changes were observed in the expression and function of the ABC-transporters MRP-1 and BCRP. It is concluded that GL-40 cells represent a useful model for studying P-gp dependent drug resistance in canine lymphoid neoplasia, and that this model can be used for screening substances as potential P-gp substrates and their capacity to modulate P-gp mediated drug resistance.

Intraperitoneal antineoplastic drug delivery: experience with a cyclophosphamide, vincristine and prednisolone protocol in cats with malignant lymphoma.

In this retrospective study, the efficacy and safety were examined for an intraperitoneal chemotherapy protocol-cyclophosphamide, vincristine and prednisolone (IP-COP) in 26 cats with malignant lymphoma. Certainly in cats fiercely resisting IV administration the IP route is a more practical method, safer for the administrator and less stressful for the cat. Complete remission (CR) rate was 76.9% (n = 20). Median duration of first remission was 421 days. Estimated 1- and 2-year disease free period were 67.1 and 48.0%, respectively. Median duration of survival was 388 days and estimated overall 1- and 2-year survival periods were 54.7 and 46.9% respectively. Young cats had a more favourable prognosis. Reaching CR was essential for long-term survival. No specific IP-related adverse events (AE) were seen. AE were generally scored as mild and were not excessively abundant. These results indicate that the IP route is a safe and effective alternative for the administration of COP protocol chemotherapeutics.

Prednisolone inclusion in a first-line multidrug cytostatic protocol for the treatment of canine lymphoma does not affect therapy results.

Chemotherapy protocols for canine lymphoma include the routine use of glucocorticoids for their lympholytic effect. However, glucocorticoids are associated with side effects (e.g. polyphagia, polyuria, and weight gain), limit the use of non-steroidal anti-inflammatory drugs, and can induce drug transporter expression that could lead to drug resistance. Despite these negative effects, there are no data to support the use of glucocorticoids as part of a multidrug chemotherapy protocol for the treatment of canine lymphoma. A prospective, randomized clinical trial was conducted in 81 dogs with multicentric lymphoma and no history of recent glucocorticoid use. All dogs were staged and treated with the same chemotherapy protocol (L-asparaginase, cyclophosphamide, doxorubicin, vincristine, and prednisolone) with half of the dogs receiving prednisolone. Both treatment groups were similar with respect to demographics, immunophenotype, and clinical stage, except for a higher number of substage b patients in the prednisolone group (5 vs. 14; P=0.015). Treatment results obtained with the initial treatment (complete response rate 75%, disease-free period 176 days) and rescue treatment (complete response rate 45%, disease-free period 133 days), overall survival (283 days) and adverse events (number and grade) were similar for both groups. In conclusion, prednisolone, as part of a multidrug chemotherapy protocol, has no additional effect on treatment results and can be omitted from first-line multidrug protocols used for the treatment of canine lymphoma.

Masitinib reverses doxorubicin resistance in canine lymphoid cells by inhibiting the function of P-glycoprotein.

Overexpression of ABC-transporters including Pgp, MRP1, and BCRP has been associated with multidrug resistance (MDR) in both human and canine oncology. Therapeutic interventions to reverse MDR are limited, but include multidrug protocols and the temporary concomitant use of inhibitors of ABC-transporters. Recently, the use of tyrosine kinase inhibitors has been proposed to overcome MDR in human oncology. One of the tyrosine kinase inhibitors, masitinib, is licensed for veterinary use in the treatment of canine mast cell tumors. Therefore, this study aimed to assess the potential of masitinib to revert MDR in canine malignant lymphoma using an in vitro model with canine lymphoid cell lines. Masitinib had a mild antiproliferative effect on lymphoid cells, inhibited Pgp function at concentrations equal to or exceeding 1 µm and was able to reverse doxorubicin resistance. The current findings provide the rationale for a combined use of masitinib with doxorubicin in the treatment of dogs with doxorubicin-resistant malignant lymphoma but await confirmation in clinical trials.

A randomized controlled study into the efficacy and toxicity of pegylated liposome encapsulated doxorubicin as an adjuvant therapy in dogs with splenic haemangiosarcoma.

Safety and efficacy of pegylated liposome encapsulated doxorubicin (PL-DOX) was compared with free doxorubicin as an adjuvant monotherapy in dogs with splenic haemangiosarcoma after splenectomy in a randomized prospective clinical trial. A total of 17 dogs in each group were treated. No significant difference in survival between the two treatments was found. The calculated median overall survival time for the 34 dogs was 166 days [95% confidence interval (CI) 148-184]. The ½ year and one-year survival was 41.2% (95% CI 24.8-56.9) and 22.7% (95% CI 9.9-37.4), respectively. In dogs treated with PL-DOX, a desquamating dermatitis like palmar-plantar erythrodysesthesia (PPES) was seen in two dogs, while three other dogs showed anaphylactic reactions. Cardiotoxicity was not seen in either treatment groups.

Recommended guidelines for the conduct and evaluation of prognostic studies in veterinary oncology.

There is an increasing need for more accurate prognostic and predictive markers in veterinary oncology because of an increasing number of treatment options, the increased financial costs associated with treatment, and the emotional stress experienced by owners in association with the disease and its treatment. Numerous studies have evaluated potential prognostic and predictive markers for veterinary neoplastic diseases, but there are no established guidelines or standards for the conduct and reporting of prognostic studies in veterinary medicine. This lack of standardization has made the evaluation and comparison of studies difficult. Most important, translating these results to clinical applications is problematic. To address this issue, the American College of Veterinary Pathologists' Oncology Committee organized an initiative to establish guidelines for the conduct and reporting of prognostic studies in veterinary oncology. The goal of this initiative is to increase the quality and standardization of veterinary prognostic studies to facilitate independent evaluation, validation, comparison, and implementation of study results. This article represents a consensus statement on the conduct and reporting of prognostic studies in veterinary oncology from veterinary pathologists and oncologists from around the world. These guidelines should be considered a recommendation based on the current state of knowledge in the field, and they will need to be continually reevaluated and revised as the field of veterinary oncology continues to progress. As mentioned, these guidelines were developed through an initiative of the American College of Veterinary Pathologists' Oncology Committee, and they have been reviewed and endorsed by the World Small Animal Veterinary Association.

Stability and reproducibility of ADVIA 120-measured red blood cell and platelet parameters in dogs, cats, and horses, and the use of reticulocyte haemoglobin content (CH(R)) in the diagnosis of iron deficiency.

Modern laser-based haematology analysers such as the ADVIA 120 have species-specific software and offer the possibility of assessing new haematological parameters. These parameters have yet to be evaluated, and as these analysers are often used in referral laboratories, it is important to know whether the values of haematological parameters change during sample transport. Therefore, samples of EDTA-anticoagulated blood from nine healthy dogs and EDTA- and citrate-anticoagulated blood from six healthy horses were collected and stored at room temperature for 72 and 48 hours, respectively. In canine samples, WBC and the red blood cell parameters Hb, Hb(cell), Ht, MCV, and MCHC changed significantly after only 24 hours of storage. Thus if canine blood samples need to be stored for 24 hours or longer, Hb, RBC, and MCH would appear to be more reliable parameters than Ht, Hb(cell), MCV, and MCHC. The cytoplasmic haemoglobin content (CH(R)) remained stable up to 48 hours. Both dog and horse platelet numbers were stable over time when blood was anticoagulated with EDTA. Of the platelet-derived parameters, MPC was already significantly lower 2 hours after collection of equine blood samples and was also significantly lower 24 hours after collection of canine blood samples. In contrast, MPV levels were significantly higher 48 hours after sample collection. Initial platelet numbers and platelet parameters were significantly different in citrate-anticoagulated blood and EDTA-anticoagulated blood, and platelet numbers and MPM decreased significantly in citrate-anticoagulated blood samples after only 4 hours of storage. After reference intervals for CH(R) had been established using samples from 53 non-anaemic dogs and 150 non-anaemic cats, the use of CH(R) to detect iron deficiency anaemia was tested in 63 dogs and 55 cats with different diseases. With the help of ROC curves, the optimal cut-off point was determined to be 1.22 fmol in dogs and 0.88 fmol in cats, resulting in a sensitivity of 95.2% and a specificity of 90.5% in dogs and 93.8% and 76.9% in cats, respectively.

Androgen receptor CAG repeat polymorphisms in canine prostate cancer.

BACKGROUND: Relatively shorter lengths of the polymorphic polyglutamine repeat-1 of the androgen receptor (AR) have been associated with an increased risk of prostate cancer (PC) in humans. In the dog, there are 2 polymorphic CAG repeat (CAGr) regions. OBJECTIVE: To investigate the relationship of CAGr length of the canine AR-gene and the development of PC. ANIMALS: Thirty-two dogs with PC and 172 control dogs were used. METHODS: DNA was extracted from blood. Both CAG repeats were amplified by polymerase chain reaction (PCR) and PCR products were sequenced. RESULTS: In dogs with PC, CAG-1 repeat length was shorter (P = .001) by an increased proportion of 10 repeats (P = .011) and no 12 repeats (P = .0017) than in the control dogs. No significant changes were found in CAG-3 length distribution. CAG-1 and CAG-3 polymorphisms proved not to be in linkage disequilibrium. Breed difference in allelic distribution was found in the control group. Of the prostate-disease sensitive breeds, a high percentage (64.5%) of the shortest haplotype 10/11 was found in the Doberman, whereas Beagles and German Pointers had higher haplotype 12/11 (47.1 and 50%). Bernese Mountain dogs and Bouvier dogs both shared a high percentage of 11 CAG-1 repeats and 13 CAG-3 repeats. Differences in (combined) allelic distributions among breeds were not significant. CONCLUSIONS AND CLINICAL IMPORTANCE: In this preliminary study, short CAG-1 repeats in the AR-gene were associated with an increased risk of developing canine PC. Although breed-specific differences in allelic distribution of CAG-1 and CAG-3 repeats were found, these could not be related to PC risk.

Preliminary results of intraoperative photodynamic therapy with 5-aminolevulinic acid in dogs with prostate carcinoma.

Six client-owned dogs with prostate carcinoma were treated with a combination of (1) partial subcapsular prostatectomy using an Nd:YAG laser, (2) intraoperative photodynamic therapy using a halogen broad band lamp after local administration of a photosensitiser, and (3) systemic treatment with meloxicam. Median survival time was 41days (range 10-68days), which compared negatively with previous reports of subtotal laser prostatectomy combined with topical interleukin-2 administration, and photodynamic therapy alone. Despite treatment, the disease progressed locally, causing signs of stranguria to recur, and in the form of distant metastases. The recurrence of clinical signs due to the primary tumour despite photodynamic therapy is probably largely explained by insufficient penetration of light into the tissue. Better results may be obtained using other light sources (e.g. laser) and alternative techniques of light delivery, such as fibres or catheters allowing interstitial diffusion of light.

Hyperthyroidism due to an intrathoracic tumour in a dog with test results suggesting hyperadrenocorticism.

The elevated urinary corticoid/creatinine ratios of an 11-year-old Jack Russell terrier with polyuria were suppressible in a high-dose dexamethasone suppression test, which was suggestive of pituitary-dependent hyperadrenocorticism. The absence of physical and routine-laboratory changes compatible with hyperadrenocorticism and the relatively high plasma thyroxine concentration were the impetus for additional studies of thyroid and adrenocortical functions. A high plasma thyroxine concentration (62 nmol/l; 5.0 microg/100 ml) suggested the presence of hyperthyroidism. Radiography, (99m)TcO(4) (-) scintigraphy, ultrasonography, computed tomography and cytology revealed a hyperfunctioning intrathoracic thyroid tumour. In the low-dose dexamethasone suppression test, the plasma cortisol concentration exceeded the reference value of 40 nmol/l (1.4 microg/100 ml) at eight hours after dexamethasone administration (0.01 mg/kg intravenously), a test result compatible with hyperadrenocorticism. In conclusion, this report represents the first case of a dog with an autonomously hyperfunctioning thyroid tumour in the thorax. The elevated urinary corticoid excretion and the positive low-dose dexamethasone suppression test may be explained by alterations in cortisol metabolism, the stress of the hyperthyroid state or both.