MRI of CNS lymphoma with choroid plexus involvement in five dogs and one cat.

OBJECTIVES: To describe the clinical features, magnetic resonance imaging (MRI) findings, and outcome of dogs and cats with central nervous system (CNS) lymphoma that involved the choroid plexus. MATERIALS AND METHODS: A bi-institutional retrospective study of MRI of dogs and cats with CNS lymphoma, in which the choroid plexus was affected on MRI. Signalment, clinical, MRI, clinicopathologic and histopathologic findings were recorded and evaluated. RESULTS: CNS lymphoma with choroid plexus involvement on the MRI was identified in five dogs and one cat. MRI revealed diffuse enlargement and multifocal nodularity in the choroid plexus in most cases, with the fourth ventricle the most common site affected. Five of the cases had signs of extraneural involvement (including the cat), while the sixth case was not staged. Four of five CSF samples analysed provided a diagnosis of lymphoma. CLINICAL SIGNIFICANCE: We report MRI findings of CNS lymphoma involving the choroid plexus. These results show the importance of recognising novel imaging patterns and the potential utility of CSF collection in diagnosing CNS lymphoma involving the choroid plexus ante mortem.

Clinical Evaluation of Tavocept to Decrease Diuresis Time and Volume in Dogs with Bladder Cancer Receiving Cisplatin.

BACKGROUND: Transitional cell carcinoma is the most common bladder cancer of dogs. Cisplatin combined with piroxicam provides superior response rates, but unacceptable rates of nephrotoxicity. Tavocept is a chemoprotectant that has mitigated cisplatin toxicity and decreased the required infusion/diuresis volume in clinical trials in humans. HYPOTHESIS/OBJECTIVES: We hypothesized that Tavocept would decrease diuresis volume and time and facilitate safe administration of a cisplatin/piroxicam protocol to dogs with bladder cancer. Secondary objectives were to compare response rate and survival times to an historical comparator group treated without Tavocept. ANIMALS: Fourteen client-owned dogs were prospectively enrolled. METHODS: Tumor volume was measured by computed tomography at days 0, 42, and 84. Dogs received combination Tavocept/cisplatin with a shortened diuresis protocol. A total of 4 doses was planned, with concurrent administration of piroxicam. Serial biochemical analyses were evaluated for azotemia. RESULTS: A 90-minute infusion/diuresis time was used for all dogs. Three dogs (21%) had concurrent increases in serum creatinine (>2.0 mg/dL) and BUN (>42 mg/dL) concentrations; 2 of these dogs were isosthenuric. This frequency of nephrotoxicity is significantly less (P = 0.0406) than that of an historical control group treated without Tavocept. Overall response rate was 27%. Median survival time was comparable to historical controls (253 vs. 246 days). CONCLUSIONS AND CLINICAL IMPORTANCE: Tavocept decreased the required diuresis time with cisplatin from > 6 hours to 90 minutes, while also decreasing occurrence of azotemia. Survival time was comparable, but the response rate was inferior to an historical comparator group. Further evaluation in other tumors susceptible to platinum agents is warranted.

Thymidine Kinase Type 1 and C-Reactive Protein Concentrations in Dogs with Spontaneously Occurring Cancer.

BACKGROUND: Serum thymidine kinase type 1 (TK1) and canine C-Reactive Protein (cCRP) might be useful in detecting dogs with cancer. Algorithms combining biomarkers are sometimes more accurate than results of individual tests. OBJECTIVES: The aim of this study was to compare serum TK1 and cCRP and Neoplasia Index (NI) in healthy and tumor-bearing dogs. ANIMALS: Client-owned dogs with (n = 253) and without (n = 156) cancer. METHODS: Retrospective case-control study. Dogs with cancer were identified after submission of samples for commercial assay and case details were retrospectively collected. Healthy dogs (control) were identified through breed groups and health status was confirmed by health questionnaire for a minimum of 6 months. Serum TK1 activity was measured using a quantitative chemiluminescent assay and serum cCRP was measured using a quantitative ELISA assay. RESULTS: TK1 activity in the cancer (n = 253) and control group (n = 156) were 7.0 µ/L (median, range <0.5 to >100) and 1.8 µ/L (median, range 0.4 to 55.3), respectively (P < .001). cCRP concentrations in the cancer and control group were 6.0 mg/L (median, range <0.5 to >50) and 1.6 mg/L (median, range 0.09 to >50), respectively (P < .001). The NI in the cancer and control group were 6.4 (median, range 0-9.9) and 0.9 (median, range 0-7.6), respectively (P < .001). ROC AUCs of the NI and TK1 for all cancers were greater than 0.8, highest for lymphoma and histiocytic sarcoma. CONCLUSIONS AND CLINICAL IMPORTANCE: Increased concentrations of TK1 and cCRP, when present in dogs with cancer, might be useful in confirming a diagnosis and monitoring response to treatment.

Serum 25-hydroxyvitamin D concentrations in dogs - correlation with health and cancer risk.

25-hydroxyvitamin D (25(OH)D) is important in bone health as well as many diseases including cancer. Supplementation may increase responsiveness of cancer cells to chemotherapy. Serum 25(OH)D, intact parathyroid hormone (iPTH) and canine C-reactive protein (c-CRP) were measured in healthy dogs and dogs with haemoabdomen. Regression analysis determined optimal 25(OH)D concentrations. In healthy dogs (n = 282), mean iPTH concentrations correlated inversely (r(2) = 0.88, P < 0.001) to 25(OH)D concentrations. Variation in both iPTH and c-CRP plateaued at 25(OH)D concentrations of 100-120 ng mL(-1) . Haemoabdomen dogs (n = 63, 43 malignant and 20 benign) had 25(OH)D concentrations ranging from 19.4 to >150 ng mL(-1) . Relative risk of cancer increased with decreasing 25(OH)D concentrations [RR = 3.9 for 25(OH)D below 40 ng mL(-1) (P = 0.0001)]. Serum 25(OH)D concentrations in dogs vary widely, and are influenced by dietary VitD content. Serum vitD measurement can identify dogs for which supplementation may improve health and response to cancer therapy.

Preclinical imaging and treatment of cancer: the use of animal models beyond rodents.

The development of novel radiopharmaceutical agents for imaging and therapy of neoplastic diseases relies on accurate and reproducible animal models. Rodent models are often used to demonstrate the proof-of-principle tracer and therapeutic agent development, but their small size can make tissue sampling challenging. The dosimetry of decay emissions in the much smaller rodent tumors do not model dosimetry in human tumors well. In addition, rodent models of cancer represent a simplified version of a very complex process. Spontaneous tumors are heterogenous and the response to intervention can be unpredictable; tumor cells can adopt alternate signaling pathways and modify their interaction with the microenvironment. These inconsistencies, while present in humans, are difficult to fully reproduce in a genetically-engineered rodent model. Companion animals, primarily dogs and cats, offer translational models that more accurately reflect the intricate nature of spontaneous neoplasia in humans. Their larger size facilitates tissue and blood sampling when needed, and allows radiopharmaceutical tracers to be studied on human-scale imaging systems to better mimic the clinical application of the agent. This article will review the growing body of literature surrounding the use of radiopharmaceutical agents for both imaging and therapy in companion dogs and cats. Previous investigations have been performed both for the advancement of routine, high-level veterinary care, and in the context of translational research from which the results of imaging and treatment can be readily applied to people. Studies utilizing the spontaneously occurring cancer model in companion animals involving positron emission tomography, radiotracers, dosimetry, theranostics, targeted radiopharmaceuticals, brachytherapy, and boron neutron capture therapy are discussed.

Serum thymidine kinase 1 and C-reactive protein as biomarkers for screening clinically healthy dogs for occult disease.

Thymidine kinase (TK1) is a biomarker that correlates well with diagnosis and prognosis in certain canine cancers. Canine C-reactive protein (cCRP) is a widely accepted marker of inflammation correlated with increased risk and severity of various diseases. We evaluated serum TK1 and cCRP concentrations in apparently healthy dogs (n = 360). All dogs were followed up for a minimum of 6 months by health questionnaire. All dogs with cancer were identified using a proprietary dual-biomarker algorithm [termed Neoplasia Index (NI)]. Specificity of positive NI is 0.91 and high positive is 0.98. All-cause mortality was 20% in dogs with elevated cCRP and 3% in dogs with low cCRP. The performance of serum TK1 and cCRP as tools for screening for occult cancer is improved when evaluated together. Serum TK1 and cCRP (unified in the NI) are useful in the screening of occult canine cancer. cCRP is useful in screening for other serious diseases.

Hemodynamic and biochemical alterations in dogs with lymphoma after induction of chemotherapy.

BACKGROUND: Doxorubicin is a common antineoplastic agent with dose-dependent cardiotoxic adverse effects, and pre-existing myocardial dysfunction is a contraindication to its use. OBJECTIVES: To systematically define the hemodynamic and biochemical alterations in dogs undergoing chemotherapy for newly diagnosed lymphoma and assess the reversibility of these alterations with fluid administration. ANIMALS: Twenty-one client-owned dogs with newly diagnosed lymphoma were evaluated 1 week after induction of chemotherapy. Underlying degenerative valve disease was exclusionary. Eighteen healthy age- and weight-matched dogs were used as controls. METHODS: Physical examination, blood pressure by Doppler, echocardiography, and biochemical evaluation (routine serum biochemistry, plasma renin activity and aldosterone concentrations, plasma and urine osmolalities, and urine electrolyte concentrations) were measured in dogs with lymphoma and compared to controls. Dogs with lymphoma received crystalloids IV at 6 mL/kg/h for 24 hours. All variables were reassessed at 4 and 24 hours. Deuterium oxide dilution and bromide dilution were used to determine total body water and extracellular water space, respectively. RESULTS: Baseline echocardiograms showed significantly smaller chamber dimensions in dogs with lymphoma compared to controls. These changes were reversed by fluid administration. Systolic blood pressure and urine sodium concentration were significantly increased, and bromide dilution space, PCV, urine specific gravity, and urine potassium concentration were significantly decreased compared to controls. CONCLUSION AND CLINICAL IMPORTANCE: Echocardiographic and biochemical abnormalities in dogs with lymphoma appear consistent with volume depletion, and may be the result of systemic hypertension and subsequent pressure natriuresis.

Safety evaluation of combination vinblastine and toceranib phosphate (Palladia®) in dogs: a phase I dose-finding study.

Combining drugs with known single-agent activity that lack overlapping dose-limiting toxicities (DLT) and exert antitumour activity through different mechanisms could improve clinical outcome. As toceranib and vinblastine meet these requisites, a phase I trial was performed in combination in dogs with mast cell tumours. The DLT for the simultaneous combination was neutropenia and the maximally tolerated dose was vinblastine (1.6 mg m(-2) every other week) concurrent with toceranib (3.25 mg kg(-1) PO, every other day). This represents greater than a 50% reduction in dose intensity for vinblastine (compared with single-agent use) and as such does not support this combination based on current drug combination paradigms. Although a strict adherence to dose paradigms speaks against the combination, evidence of significant activity (71% objective response) and enhanced myelosuppression suggest additive or synergistic activity. A prospective randomized evaluation comparing this combination with standard single-agent treatments would seem prudent to interrogate this potential.

Outcome of 19 dogs with parathyroid carcinoma after surgical excision.

Parathyroid carcinoma (PTC) is rare in dogs and there is little information documenting its treatment and prognosis. The objective of this study was to describe the outcome of dogs with PTC treated with surgical excision. Medical records of 19 dogs undergoing surgical excision of PTC between 1990 and 2010 were reviewed retrospectively. Dogs were presented for clinical hypercalcaemia or incidental hypercalcaemia noted by referring veterinarians on routine serum chemistry profiles. A parathyroid nodule was identified with cervical ultrasound in 17/17 dogs. Hypercalcaemia resolved in 18/19 dogs within 4 days postoperatively. Nine developed hypocalcaemia. None were confirmed to develop recurrent or metastatic PTC. The only death associated with PTC was a dog that was euthanized for intractable hypocalcaemia 9 days after surgery. Estimated 1-, 2- and 3-year survival rates were 72, 37 and 30%, respectively. Excision of PTC results in resolution of hypercalcaemia and excellent tumour control.

Elevated serum thymidine kinase activity in canine splenic hemangiosarcoma*.

Thymidine kinase 1 (TK1) is a soluble biomarker associated with DNA synthesis. This prospective study evaluated serum TK1 activity in dogs presenting with hemoabdomen and a splenic mass. An ELISA using azidothymidine as a substrate was used to evaluate TK1 activity. Sixty-two dogs with hemoabdomen and 15 normal controls were studied. Serum TK1 activity was significantly higher in dogs with hemangiosarcoma (HSA) than in normal dogs (mean ± SEM = 17.0 ± 5.0 and 2.01 ± 0.6, respectively), but not dogs with benign disease (mean ± SEM = 10.0 ± 3.3). Using a cut-off of 6.55 U/L, TK activity demonstrated a sensitivity of 0.52, specificity of 0.93, positive predictive value of 0.94 and negative predictive value of 0.48 for distinguishing HSA versus normal. When interval thresholds of <1.55 and >7.95 U/L were used together, diagnostic utility was increased. Serum TK1 evaluation may help to discriminate between benign disease and HSA in dogs with hemoabdomen and a splenic mass.

An open-label, dose-escalating phase I study of elsamitrucin (SPI 28090) in treatment of malignant solid tumors in dogs.

BACKGROUND: Elsamitrucin, the most potent topoisomerase II inhibitor available, is unique in that it does not cause neutropenia or cardiotoxicosis. It has antitumor activity in human patients with relapsed or refractory non-Hodgkin's lymphoma. OBJECTIVES: To determine the maximum tolerated dose (MTD), safety, and toxicity of elsamitrucin when administered to tumor-bearing dogs and to evaluate the incidence and severity of adverse events. ANIMALS: Twenty client-owned dogs with spontaneous malignant solid tumors or lymphoma that were refractory to, or for which the owner declined, conventional therapy were enrolled. METHODS: Prospective, open-label, single-agent study. Escalating doses of elsamitrucin were administered once weekly i.v. for up to 16 weeks in a modified 3 + 3 Phase I design. The starting dose was 0.06 mg/kg with escalation to 0.08 and 0.09 mg/kg. Dogs that remained on the study were monitored for evidence of toxicoses for at least 4 weeks and for survival every 2 months. RESULTS: Serious adverse events (SAEs) possibly attributable to elsamitrucin include: 1 dog developed heart failure and another developed hepatotoxicosis manifested by increased alanine aminotransferase, alkaline phosphatase, and total bilirubin (0.06 mg/kg dose); 1 dog developed severe anorexia and diarrhea, another developed severe diarrhea alone, and a 3rd dog went into cardiac arrest (0.09 mg/kg dose). A dose of 0.08 mg/kg was well tolerated with no SAEs. CONCLUSIONS AND CLINICAL IMPORTANCE: The MTD and recommended dose for Phase II trials of elsamitrucin is 0.08 mg/kg i.v. weekly. Elsamitrucin might be considered for combination protocols with myelosuppressive chemotherapy agents.

Evaluation of satraplatin in dogs with spontaneously occurring malignant tumors.

BACKGROUND: Satraplatin is the 1st orally bioavailable platinum anticancer drug. OBJECTIVE: Our objectives were to evaluate efficacy in vitro against a canine cancer cell line, to determine the maximally tolerated dose (MTD) of satraplatin in tumor-bearing dogs, to identify the dose-limiting and other toxicities in dogs, and to record pharmacokinetics (PK). ANIMALS: Dogs with macro- or microscopic malignant neoplasia. METHODS: D17 canine osteosarcoma cells first were evaluated in a clonogenic survival assay. Then, dogs with a diagnosis of malignant neoplasia were prospectively entered in standard 3 + 3 cohorts. Additional patients were entered at the MTD to assess efficacy. Total and free platinum (by ultrafiltrate) concentrations were determined with inductively coupled plasma mass spectroscopy. RESULTS: Satraplatin inhibited clonogenic survival in vitro at clinically relevant and achievable concentrations. Twenty-three dogs were treated, 14 with PK evaluation. The MTD was 35 mg/m(2)/d for 5 days, repeated every 3-4 weeks. Bioavailability was 41%. PK variables (mean ± SD) at the MTD included T(max) 1.8 (± 0.7) hours, C(max) 72 (± 26) ng/mL, area under concentration (AUC)(0-24 h) 316 (± 63) h × ng/mL, and MRT 7 (± 1.3) hours. Higher AUC after the 5th versus the 1st dose suggested drug accumulation. Interestingly, platelets consistently reached nadir sooner than did neutrophils (day 14 versus 19). Myelosuppression was dose-limiting and gastrointestinal toxicity was mild. CONCLUSIONS AND CLINICAL IMPORTANCE: Satraplatin was well tolerated in tumor-bearing dogs, thus warranting further investigation in a phase II trial.

Immunohistochemical detection of retinoid receptors in tumors from 30 dogs diagnosed with cutaneous lymphoma.

BACKGROUND: Retinoids exert their effects by binding to retinoid receptors. Two types of retinoid receptors have been described: retinoic acid receptor (RAR) and retinoid X receptor (RXR), and their subtypes α, ß, and γ. The expression of subtypes varies depending on the disease process. This study intended to detect the pattern of retinoid receptor expression in cutaneous lymphomas in dogs. HYPOTHESIS: Cutaneous lymphomas in dogs have variable expression of retinoid and retinoid X receptors. ANIMALS: Biopsy specimens from 30 dogs with cutaneous lymphoma. METHODS: Tissues of dogs with cutaneous lymphoma were evaluated by immunohistochemistry for expression of retinoid receptors. The tissues were tested for the presence of 3 RAR and RXR subtypes (α, ß, and γ). Lymphoma immunophenotype was determined by the use of the immunohistochemical markers CD79a (B-cell) and CD3 (T-cell) in all cases. RESULTS: Twenty-nine of 30 dogs were CD3 positive. The retinoid receptors expressed with the greatest frequency were RARß (87% of cases), and RXRα and RXRγ (77% of cases). The expression of RARγ was not observed. CONCLUSIONS AND CLINICAL RELEVANCE: Retinoid and rexinoid receptor binding drugs may have an impact on the treatment of dogs with cutaneous lymphoma.

Response evaluation criteria for peripheral nodal lymphoma in dogs (v1.0)--a Veterinary Cooperative Oncology Group (VCOG) consensus document.

Standardized assessment of response to therapy for lymphoma in dogs is lacking, making critical comparisons of treatment protocols difficult. This Veterinary Cooperative Oncology Group (VCOG) consensus document, based on the recommendations of a subcommittee of ACVIM board-certified veterinary oncologists, was unanimously adopted at the 29th Annual Conference of the Veterinary Cancer Society (VCS) by the VCOG membership. It has integrated guidance from the response assessment criteria established for lymphoma in human patients using standards available in routine veterinary oncology practices that are simple, repeatable and consistently applicable. These guidelines are intended only for use in dogs, where peripheral lymphadenopathy represents the principal component of their disease and as such do not critically assess extranodal disease (e.g., primary cutaneous, central nervous system, gastrointestinal). It is hoped these guidelines will be widely adopted and serve to facilitate the comparison of current and future treatment protocols used in the therapy of dogs.

Cloning and expression of canine CD25 for validation of an anti-human CD25 antibody to compare T regulatory lymphocytes in healthy dogs and dogs with osteosarcoma.

T regulatory cells (Tregs) are a unique subset of T helper cells that serve to modify/inhibit effector cells of the immune system and thus are essential to prevent autoimmunity. Overzealous Treg activity may contribute to impaired immune responses to cancer. Tregs can be phenotypically identified by proteins expressed on the cell surface (CD4 and CD25) and inside the cell (forkhead box3 (FoxP3)), although in dogs, no anti-canine CD25 antibody exists. We hypothesized that a mouse anti-human CD25 antibody definitively recognizes the canine protein and can be used to identify Tregs in dogs. We describe cloning and transfection of the canine CD25 gene into human HeLa cells with subsequent expression of the canine protein on the cell surface detected using an anti-human CD25 antibody in a flow cytometric assay. Validation of this antibody was used to identify CD4+CD25+FoxP3+ Tregs in 39 healthy dogs and 16 dogs with osteosarcoma (OSA). Results were expressed in five different ways and showed significantly fewer %CD4+CD25+ T lymphocytes expressing FoxP3 in blood of older dogs (>/=7 years) compared with the other two age groups (<2 and 2-6 years) (p<0.001) and fewer %CD4+CD25+FoxP3+ Tregs in the tumor draining lymph nodes of OSA patients compared to the unrelated lymph node (p=0.049). However, there was no significant difference in % Tregs in the peripheral blood or lymph nodes between the control dogs and those with OSA. While the CD25 antibody can be successfully used in a flow cytometric assay to identify Tregs, this study does not support clinical utility of phenotypic recognition of Tregs in dogs with OSA.

Echocardiographic assessment of hemodynamic changes produced by two methods of inducing fluid deficit in dogs.

BACKGROUND: Hydration status is important to the cardiovascular system because of its effects on preload. Decreased preload can alter echocardiographic measurements of systolic and diastolic function, potentially confounding interpretation of results. HYPOTHESIS/OBJECTIVES: Mild fluid deficits are associated with measurable echocardiographic changes that are validated by physical and biochemical markers of decreased intravascular volume. ANIMALS: Twenty-five healthy staff/student-owned dogs with no evidence of cardiac or renal disease. METHODS: Prospective, interventional laboratory study. Dogs were randomly assigned to water deprivation (WD) alone for 8 hours (n = 13) or to furosemide treatment (FTx, 2.5mg/kg IV) followed by WD for 8 hours (n = 12). Echocardiograms, biochemical sampling, and physical parameters were measured at baseline, and after 4 and 8 hours. RESULTS: Both protocols induced fluid deficit as indicated by significant (P < .00001) decreases in weight at 4 hours (WD, 1.1%; FTx, 3.7%) and 8 hours (WD, 2.7%; FTx, 4.5%). Furosemide significantly decreased left ventricular end-diastolic volume (54.3 +/- 19.3-42.1 +/- 17.3 mL, P < .0001), cardiac index (4.2 +/- 1.1-2.9 +/- 0.9 L/min/M2, P < .0001), and mitral valve E wave velocity (0.79 +/- 0.2-0.66 +/- 0.2 m/s, P = .0004). These changes were accompanied by significant increases in blood urea nitrogen concentration (13.8 +/- 2.6-14.8 +/- 2.7 mg/dL, P = .04), vasopressin concentration (1.4 +/- 1.2-3.3 +/- 1.9 pg/mL, P = .045), and PCV (49.8 +/- 4.5-53.2 +/- 6.5%, P = .006). Effects of water deprivation alone were similar, but less pronounced. CONCLUSIONS AND CLINICAL IMPORTANCE: Mild fluid deficits have measurable hemodynamic effects in dogs. Hydration status should be considered when evaluating cardiac function by echocardiogram.

Cardiac troponin I in canine patients with lymphoma and osteosarcoma receiving doxorubicin: comparison with clinical heart disease in a retrospective analysis.

The cumulative cardiotoxicity that occurs as a result of doxorubicin chemotherapy is irreversible and can affect both quality and quantity of life for the cancer patient. Cardiac troponin I (cTnI) is a sensitive and specific marker of cardiomyocyte death. The purpose of this retrospective study was to evaluate serum concentrations of cTnI in dogs with lymphoma or osteosarcoma given doxorubicin chemotherapy, and with known cardiac outcome, based on a minimum assessment by physical examination and thoracic radiography. Serum samples were also available for cTnI measurement from seven healthy dogs given intracoronary doxorubicin. Serial serum samples obtained before, during and after doxorubicin chemotherapy showed increased cTnI concentrations in some clinical patients following chemotherapy (P = 0.0083 compared to baseline), but this did not correlate with clinical signs of cardiomyopathy. In dogs that subsequently developed cardiomyopathy however, serum cTnI concentrations were elevated before clinical signs became evident (confirmed with echocardiography).

Serum alhpa 1-acid glycoprotein concentrations in healthy and tumor-bearing cats.

The purpose of this study was to evaluate alpha 1-acid glycoprotein (AGP) concentrations in tumor-bearing and healthy cats. The hypothesis of the present study was that AGP concentrations would be significantly increased in tumor-bearing cats. Serum from 51 healthy and 97 tumor-bearing, client-owned cats was harvested at the time of presentation and stored at -80 degrees C until assayed. Cats with measurable, histologically confirmed malignancies, and healthy cats of similar ages were included. Serum was assayed for AGP concentration by using a radial immunodiffusion method. AGP concentrations were significantly (P = .0051) higher in tumor-bearing (763 +/- 595 microg/mL; mean +/- SD) when compared to healthy cats (501 +/- 377 microg/mL; mean +/- SD). Of the tumor-bearing cats, 35 had carcinomas, 33 had sarcomas, and 26 had discrete, round cell tumors. AGP concentrations were 645 +/- 62 microg/mL, 660 +/- 540 microg/mL, and 967 +/- 860 microg/mL, respectively, and there were no significant differences among the groups.

Idiopathic thrombocytopenic purpura in a cat.

An 11-year-old, castrated, male domestic shorthair cat was presented for hematuria and pollakiuria. The cat had a marked thrombocytopenia, and a bone-marrow core biopsy demonstrated megakaryocytic hyperplasia with many megakaryocyte-associated neutrophils (i.e., emperipolesis). On peripheral blood, collected at initial presentation, what appeared to be platelets were noted to be within or adherent to occasional neutrophils. The thrombocytopenia was idiopathic in that no definitive cause could be found. However, platelet concentrations appeared to increase and decrease in response to changes in prednisone and cyclosporine therapy, suggesting a possible immune-mediated pathogenesis. As tests to detect increased feline platelet-associated antibodies are unavailable, immune-mediated thrombocytopenia can only be tentatively diagnosed in cats by exclusion and response to therapy.