Cardiac Rhabdomyoma in Four Göttingen Minipigs.

Göttingen minipigs are increasingly used as an alternative large animal model in nonclinical toxicology studies, and proliferative lesions in this species are rare. Here, we report four cases of cardiac rhabdomyoma in Göttingen minipigs, an incidental and benign mass in the heart. Three cases lacked gross observations and had a microscopic nodule in either the left ventricle or interventricular septum. The last case had a large, firm, raised nodule on a left ventricular papillary muscle noted at necropsy, with additional microscopic intramural masses in the left ventricular wall. In all cases, microscopic evaluation revealed well-circumscribed, expansile nodules composed of bundles of large, highly vacuolated, ovoid to polygonal cells with variable cytoplasmic processes radiating from a centrally located nucleus. Cells displayed patchy accumulation of intracytoplasmic, PAS-positive material and haphazardly arranged cytoplasmic cross-striations. There was no evidence of cardiac insufficiency or other data to suggest the masses were clinically meaningful. Cardiac rhabdomyomas have been reported in meat-hybrid swine, with a breed predisposition in red wattle. This lesion is well established in guinea pigs, but documentation in other laboratory species used in toxicologic studies is limited to two beagle dogs. To our knowledge, this is the first report of spontaneous cardiac rhabdomyoma in Göttingen minipigs.

Diffuse Small B-Cell Lymphoma: A High-Grade Malignancy.

The most common subtype of lymphoma in the dog is diffuse large B-cell lymphoma (DLBCL). The remaining forms of B-cell lymphoma in dogs are categorized as small-to-intermediate in size and include marginal zone, follicular, mantle cell, and small-cell lymphocytic lymphoma. Marginal zone lymphoma and follicular lymphoma have readily identifiable unique histologic features while other forms of small B-cell lymphoma in the dog are poorly described by histopathology. Forty-seven cases of nodal small B-cell lymphoma identified by flow cytometry (small cell size based on forward scatter) with concurrent histopathology were reviewed. These cases fell into 3 histologic subtypes: marginal zone lymphoma, follicular lymphoma, and a diffuse form of small B-cell lymphoma with consistent features. As a descriptive term, we refer to the latter subtype as diffuse small B-cell lymphoma (DSBCL) until it can be further characterized by gene expression profiling and other molecular tools. Clinical presentation of DSBCL was compared to cases of histologically confirmed DLBCL and clinical follow-up was obtained for 22 of the 27 cases of DSBCL. This subset of diffuse small B-cell lymphoma had an overall median survival of 140 days. The expression of CD21, class II MHC and CD25 by flow cytometry did not differ between DSBCL and the other histologic subtypes of small cell B-cell lymphoma making histopathology the only current method of classification.

Role of Periostin Expression in Canine Osteosarcoma Biology and Clinical Outcome.

Periostin is a matricellular protein important in regulating bone, tooth, and cardiac development. In pathologic conditions, periostin drives allergic and fibrotic inflammatory diseases and is also overexpressed in certain cancers. Periostin signaling in tumors has been shown to promote angiogenesis, metastasis, and cancer stem cell survival in rodent models, and its overexpression is associated with poor prognosis in human glioblastoma. However, the role of periostin in regulating tumorigenesis of canine cancers has not been evaluated. Given its role in bone development, we sought to evaluate mRNA and protein expression of periostin in canine osteosarcoma (OS) and assess its association with patient outcome. We validated an anti-human periostin antibody cross-reactive to canine periostin via western blot and immunohistochemistry and evaluated periostin expression in microarray data from 49 primary canine OS tumors and 8 normal bone samples. Periostin mRNA was upregulated greater than 40-fold in canine OS tumors compared to normal bone and was significantly correlated with periostin protein expression based on quantitative image analysis. However, neither periostin mRNA nor protein expression were associated with time to metastasis in this cohort. Gene Set Enrichment Analysis demonstrated significant enhancement of pro-tumorigenic pathways including canonical WNT signaling, epithelial-mesenchymal transition, and angiogenesis in periostin-high tumors, while periostin-low tumors demonstrated evidence of heightened antitumor immune responses. Overall, these data identify a novel antibody that can be used as a tool for evaluation of periostin expression in dogs and suggest that investigation of Wnt pathway-targeted drugs in periostin overexpressing canine OS may be a potential therapeutic target.

Skull Base Primary Extracranial Meningioma with Hyperostosis in a Small Mixed-Breed Dog.

A 7 yr old female spayed Chihuahua-terrier mix was presented for a progressive dry, hacking cough over 9 mo, with dyspnea aggravated by eating and drinking. Computed tomography of the skull revealed a large mineral attenuating mass associated with the left skull base, without intracranial involvement. A modified ventral paramedian hypophysectomy approach along the medial aspect of the left ramus was used to approach the base of the skull. Ninety percent of the mass was debulked via high-speed pneumatic burr. Histopathology was consistent with hyperostosis originating from a primary extracranial meningioma (ECM), with the tissue staining positive for vimentin and negative for cytokeratin. The patient was symptom free for 9 mo before clinical signs returned because of tumor recurrence and was euthanized 11 mo postoperation because of diminished quality of life. ECM is uncommonly reported in the dog, and to the authors' knowledge has not previously been reported with hyperostosis or located along the skull base at the level of the tympanic bulla. Additionally, although hyperostosis predominantly occurs as diffuse bone thickening adjacent to a meningioma, proliferative focal hyperostosis is uncommon. Given the findings in this patient, ECM should be considered as a differential diagnosis for osseous skull base masses.

Unfolding the diagnosis of subspectacular fluid opacity in a corn snake (Pantherophis guttatus).

OBJECTIVE: To present the results of clinical, surgical, and histopathologic procedures and how these were compared with the initial presumptive clinical diagnosis in a corn snake (Pantherophis guttatus) presenting with subspectacular fluid opacity; and to improve upon currently established surgical enucleation techniques in the snake. ANIMAL STUDIED: An 8-month-old corn snake was presented for enlarged globe OD. PROCEDURES: The following diagnostics were performed: systemic and ophthalmic examinations, complete blood count, cytology and culture of subspectacular fluid, and histopathology of enucleated globe and spectacle. Enucleation was performed in a routine fashion with the addition of a porcine small intestinal submucosa bioscaffold graft (SISplus™; Avalon Medical, Stillwater, MN), sutured over the orbit. RESULTS: Systemic examination revealed signs of maxillary stomatitis. Ophthalmic examination revealed semitransparent fluid in the subspectacular space. Complete blood count was unremarkable. Cytology of fluid obtained via subspectacular centesis was acellular, and culture grew Clostridium perfringens, which was consistent with the clinical suspicion of right maxillary stomatitis. Histopathology of the enucleated globe revealed spectaculitis, characterized by regional heterophilic inflammation, and no evidence of lymph dissection in the (peri)ocular tissues. The final diagnosis was a subspectacular abscess. Follow-up revealed that the SIS graft provided excellent healing and cosmesis of the surgical site. CONCLUSIONS: While there are reports of lymphatic fluid dissection between skin layers during ecdysis, which can result in an opaque spectacle, the fluid opacity in this case was attributed to a subspectacular abscess secondary to an ascending oral infection. Addition of biological wound dressing may contribute to positive post-enucleation outcome in the snake.

Lateral manus translation for limb-sparing surgery in 18 dogs with distal radial osteosarcoma in dogs.

OBJECTIVE: To describe and report outcomes after lateral translation of the manus for limb-sparing management of distal radial osteosarcoma in dogs. STUDY DESIGN: Retrospective case series. STUDY POPULATION: Eighteen client-owned dogs. METHODS: The distal aspect of the affected radius and associated neoplastic tissues were excised. The distal aspect of the ulna was preserved except for its medial cortex, which was removed en bloc with the radial segment. The manus was translated laterally to place the radial carpal bone in contact with the distal aspect of the ulna. A limb-sparing or locking compression plate was placed on the remaining proximal radius and the 3rd metacarpal bone. A 3.5-mm SOP (string of pearls) plate was placed on the lateral aspect of the proximal ulna and the 4th metacarpal bone. Dogs were administered chemotherapy. Data were collected to assess surgical and oncologic outcomes. Limb function was subjectively assessed. RESULTS: The percentage of radius removed ranged from 43% to 94% (median 54%). Complications developed in 12 limbs, with infection in 10, biomechanical complications in 6, and local recurrence in 4. Limb function was subjectively assessed as acceptable. Median disease-free interval was 219 days, and median survival time was 370 days. CONCLUSION: Outcomes after lateral translation of the manus compared favorably to other limb-sparing techniques for dogs with distal radial osteosarcoma, particularly in dogs requiring excision of a large segment of the radius. CLINICAL SIGNIFICANCE: The lateral manus translation provides an alternative limb-sparing technique that does not require an allograft, endoprosthesis, or autograft.

Pilot study utilizing Fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography for glycolytic phenotyping of canine mast cell tumors.

The goal of this prospective pilot study was to use naturally occurring canine mast cell tumors of various grades and stages as a model for attempting to determine how glucose uptake and markers of biologic behavior are correlated. It was hypothesized that enhanced glucose uptake, as measured by 2-[fluorine-18]fluoro-d-glucose-positron emission tomography/computed tomography (F18 FDG PET-CT), would correlate with histologic grade. Dogs were recruited for this study from a population referred for treatment of cytologically or histologically confirmed mast cell tumors. Patients were staged utilizing standard of care methods (abdominal ultrasound and three view thoracic radiographs), followed by a whole body F18 FDG PET-CT. Results of the F18 FDG PET-CT were analyzed for possible metastasis and standard uptake value maximum (SUVmax ) of identified lesions. Incisional or excisional biopsies of the accessible mast cell tumors were obtained and histology performed. Results were then analyzed to look for a possible correlation between the grade of mast cell tumors and SUVmax . A total of nine animals were included in the sample. Findings indicated that there was a correlation between grade of mast cell tumors and SUVmax as determined by F18 FDG PET-CT (p-value = 0.073, significance ≤ 0.1). Based on the limited power of this study, it is felt that further research to examine the relationship between glucose utilization and biologic aggressiveness in canine mast cell tumors is warranted. This study was unable to show that F18 FDG PET-CT was a better staging tool than standard of care methods.

Expression of Phosphorylated KIT in Canine Mast Cell Tumor.

Canine cutaneous mast cell tumor (MCT) is the most common canine skin tumor and exhibits variable biologic behavior. Signaling through the KIT receptor tyrosine kinase promotes cellular proliferation and survival and has been shown to play a role in MCT progression. Despite investigations into numerous biomarkers and the proposal of several grading schemas, no single marker or grading system can accurately predict outcome in canine MCT. The first aim of this study was to develop an immunohistochemical assay to measure phosphorylated KIT (pKIT) to investigate its association with 2 commonly used grading systems and other established prognostic markers for canine MCT. Thirty-four archived MCTs were evaluated for expression of pKIT and Ki-67, KIT localization, mitotic count, mutations in exons 8 and 11 in c-kit, and grading by the Patnaik and 2-tier systems. Expression of pKIT was significantly ( P < .05) correlated with the 2-tier grading scheme and c-kit mutation. Correlation approached significance ( P = .06) with Mitotic Index (MI) and Ki-67. An additional aim was to determine whether pKIT labeling provides a pharmacodynamic marker for predicting response to the receptor tyrosine kinase inhibitor toceranib (TOC). MCTs from 4 of 7 patients demonstrated a partial response to TOC. pKIT expression was assessed by immunohistochemistry in biopsies obtained before and 6 hours after the patients were treated with TOC. Reduced pKIT expression after TOC treatment was demonstrated in 3 of the 4 patients with a partial response compared to 1 of the 3 nonresponders. Collectively, these results demonstrate that immunohistochemical detection of pKIT may be a clinically relevant assay to evaluate the activation status of the major oncogenic pathway in canine MCT.

Canine and feline retinal lymphoma: a retrospective review of 12 cases.

This retrospective study identified 12 cases (6 canine and 6 feline) of ocular lymphoma with extensive retinal involvement and relative sparing of other ocular tissues. Our objectives were to describe the morphologic and immunohistochemical features of retinal lymphoma, assess the degree of correlation to the human counterpart, assign subtypes based on the veterinary-adapted WHO classification system, and promote accurate reporting of retinal involvement in cases of intraocular lymphoma. Our findings suggest that a distinct retinal tropism is quite rare, representing approximately 1% of all cases of canine and feline ocular lymphoma. No breed or sex predispositions were identified. The mean age of the affected animal was 7 years (range 4-10) and 11 years (range 6-19) for dogs and cats, respectively. Nine cases (5 canine and 4 feline) were classified as diffuse large B-cell lymphoma (DLBCL) subtype. The remaining cases were classified as peripheral T-cell lymphoma (PTCL).

Pathologic and cardiovascular characterization of pheochromocytoma-associated cardiomyopathy in dogs.

Pheochromocytoma-associated catecholamine-induced cardiomyopathy is a well-known entity in man, nonhuman primates, and mice but has not been described in dogs. In this retrospective study, 9 dogs were identified with pheochromocytomas and concurrent cardiovascular pathology observed histologically (n = 6), echocardiographically (n = 4), and/or electrocardiographically (n = 5). Cardiac lesions included multifocal cardiomyocyte necrosis with contraction bands, cardiomyocyte degeneration, myocardial hemorrhage, lymphohistiocytic myocarditis, and interstitial fibrosis. Clinical procedures, including electrocardiographic and echocardiographic examinations, Doppler blood pressure measurement, and auscultation, were available for 5 dogs and consistently revealed concentric or mixed (eccentric and concentric) ventricular hypertrophy. Additional changes observed included arrhythmias, systemic hypertension, and heart murmurs. The myocardial lesions observed in this series of dogs are similar to those observed in humans with pheochromocytoma-associated catecholamine-induced cardiomyopathy. Since the clinical manifestations of catecholamine-induced cardiac disease are amenable to medical treatment, recognition of this cardiomyopathy has the potential to reduce morbidity and mortality in dogs with pheochromocytoma.

Radiofrequency Probe and Sharp Transection for Tenoscopic-Guided Desmotomy of the Accessory Ligament of the Superficial Digital Flexor Tendon.

OBJECTIVE: To compare intra and postoperative clinical features of desmotomy of the accessory ligament of the superficial digital flexor tendon (ALSDFT) using the Saber radiofrequency (SaberRF) electrosurgical probe versus sharp transection with a tenotomy knife. STUDY DESIGN: Randomized, controlled, blocked (horse) design. ANIMALS: Adult horses (n = 6). METHODS: Each horse received bilateral, tenoscopic-guided ALSDFT desmotomy with a SaberRF and tenotomy knife, randomly assigned to left, or right limb. The desmotomy duration and intraoperative hemorrhage grades were recorded. Postoperatively, the grades for surgical incision, carpal sheath effusion, carpal range of motion, flexion pain, and lameness were recorded. Light microscopy using hematoxylin and eosin, and viability staining were performed on the ALSDFT, flexor carpi radialis tendon, radial head of the deep digital flexor tendon, and the deep digital flexor tendon. Variables were compared between desmotomy methods with a paired t-test, Wilcoxon signed rank test, or a repeated measures mixed model. Statistical significance was set at P < .05. RESULTS: Desmotomy of the ALSDFT was completed in all horses. Only mild hemorrhage was observed and not different between methods (SaberRF 2/5 limbs; tenotomy knife 5/6 limbs, P = .078). Carpal sheath effusion was greater for SaberRF at Day 1 (P = .019) but not different from tenotomy knife at any later time. There was no significant difference between methods for viability staining or other measured outcomes. CONCLUSIONS: Tenoscopic-guided ALSDFT desmotomy with the SaberRF probe showed no difference in measured outcomes to sharp transection with a tenotomy knife and minimal collateral tissue damage was observed.

Histologic characteristics and KIT staining patterns of equine cutaneous mast cell tumors.

Mast cell tumors are uncommon in horses and typically have a benign clinical course, but there are occasional reports of more aggressive behavior. The objective of this study was to review histologic features and KIT expression patterns of 72 previously diagnosed equine cutaneous mast cell tumors to determine if either is associated with clinical outcomes. Biopsy specimens were reviewed using histologic criteria derived from grading schemes, and KIT antibody expression patterns used in canine tumors and surveys were sent to referring veterinarians for follow-up clinical data. Arabians were overrepresented relative to the reference population. Most tumors were well differentiated with low mitotic rates (96%), and aberrant KIT staining patterns, as described in dogs, were uncommonly identified (12%). Associated clinical disease was uncommon and no tumors exhibited malignant behavior. Overall, KIT staining pattern and histologic features were not associated with poor clinical outcome or abnormal tumor behavior.

An in vivo ovine model of bone tissue alterations in simulated microgravity conditions.

Microgravity and its inherent reduction in body-weight associated mechanical loading encountered during spaceflight have been shown to produce deleterious effects on important human physiological processes. Rodent hindlimb unloading is the most widely-used ground-based microgravity model. Unfortunately, results from these studies are difficult to translate to the human condition due to major anatomic and physiologic differences between the two species such as bone microarchitecture and healing rates. The use of translatable ovine models to investigate orthopedic-related conditions has become increasingly popular due to similarities in size and skeletal architecture of the two species. Thus, a new translational model of simulated microgravity was developed using common external fixation techniques to shield the metatarsal bone of the ovine hindlimb during normal daily activity over an 8 week period. Bone mineral density, quantified via dual-energy X-ray absorptiometry, decreased 29.0% (p < 0.001) in the treated metatarsi. Post-sacrifice biomechanical evaluation revealed reduced bending modulus (-25.8%, p < 0.05) and failure load (-27.8%, p < 0.001) following the microgravity treatment. Microcomputed tomography and histology revealed reduced bone volume (-35.9%, p < 0.01), trabecular thickness (-30.9%, p < 0.01), trabecular number (-22.5%, p < 0.05), bone formation rate (-57.7%, p < 0.01), and osteoblast number (-52.5%, p < 0.001), as well as increased osteoclast number (269.1%, p < 0.001) in the treated metatarsi of the microgravity group. No significant alterations occurred for any outcome parameter in the Sham Surgery Group. These data indicate that the external fixation technique utilized in this model was able to effectively unload the metatarsus and induce significant radiographic, biomechanical, and histomorphometric alterations that are known to be induced by spaceflight. Further, these findings demonstrate that the physiologic mechanisms driving bone remodeling in sheep and humans during prolonged periods of unloading (specifically increased osteoclast activity) are more similar than previously utilized models, allowing more comprehensive investigations of microgravity-related bone remodeling as it relates to human spaceflight.

HES1, a target of Notch signaling, is elevated in canine osteosarcoma, but reduced in the most aggressive tumors.

BACKGROUND: Hairy and enhancer of split 1 (HES1), a basic helix-loop-helix transcriptional repressor, is a downstream target of Notch signaling. Notch signaling and HES1 expression have been linked to growth and survival in a variety of human cancer types and have been associated with increased metastasis and invasiveness in human osteosarcoma cell lines. Osteosarcoma (OSA) is an aggressive cancer demonstrating both high metastatic rate and chemotherapeutic resistance. The current study examined expression of Notch signaling mediators in primary canine OSA tumors and canine and human osteosarcoma cell lines to assess their role in OSA development and progression. RESULTS: Reverse transcriptase - quantitative PCR (RT-qPCR) was utilized to quantify HES1, HEY1, NOTCH1 and NOTCH2 gene expression in matched tumor and normal metaphyseal bone samples taken from dogs treated for appendicular OSA at the Colorado State University Veterinary Teaching Hospital. Gene expression was also assessed in tumors from dogs with a disease free interval (DFI) of <100 days compared to those with a DFI > 300 days following treatment with surgical amputation followed by standard chemotherapy. Immunohistochemistry was performed to confirm expression of HES1. Data from RT-qPCR and immunohistochemical (IHC) experiments were analyzed using REST2009 software and survival analysis based on IHC expression employed the Kaplan-Meier method and log rank analysis. Unbiased clustered images were generated from gene array analysis data for Notch/HES1 associated genes. Gene array analysis of Notch/HES1 associated genes suggested alterations in the Notch signaling pathway may contribute to the development of canine OSA. HES1 mRNA expression was elevated in tumor samples relative to normal bone, but decreased in tumor samples from dogs with a DFI < 100 days relative to those with a DFI > 300 days. NOTCH2 and HEY1 mRNA expression was also elevated in tumors relative to normal bone, but was not differentially expressed between the DFI tumor groups. Survival analysis confirmed an association between decreased HES1 immunosignal and shorter DFI. CONCLUSIONS: Our findings suggest that activation of Notch signaling occurs and may contribute to the development of canine OSA. However, association of low HES1 expression and shorter DFI suggests that mechanisms that do not alter HES1 expression may drive the most aggressive tumors.

Apoptosis in normal and Coxiella burnetii-infected placentas from Alaskan northern fur seals (Callorhinus ursinus).

In 2010, Coxiella burnetii was identified in 75% of northern fur seal placentas from a single rookery in Alaska, but nothing was known about the significance of this organism in the population. Although many infectious organisms cause increased cell death, C. burnetii has been shown to suppress apoptosis of the host macrophages as an intracellular survival mechanism. To determine if infection induces a similar functional change in the placenta, immunohistochemistry for antibodies to cleaved caspase-3 (activated caspase-3) and the (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL) technique were used to compare the amount of placental apoptosis in infected and noninfected placentas. There was a statistically significant difference in the frequency of apoptotic cells between infected and uninfected placentas, with more apoptosis identified in the uninfected placentas. This finding suggests that the survival mechanism of C. burnetii in host macrophages to reduce apoptosis may also be utilized in trophoblasts. The significance of decreased trophoblastic apoptosis for the northern fur seal fetus requires further investigation.

Primary primitive neuroectodermal tumors of the retina and ciliary body in dogs.

We describe the clinical, histological, and immunohistochemical features of primary intraocular primitive neuroectodermal tumors in eight dogs. Four of eight tumors exhibited histological features similar to human retinoblastomas characterized by Flexner-Wintersteiner rosettes, and fleurettes, and demonstrated variable immunoreactivity for retinal markers opsin, S-antigen (S-Ag) and interphotoreceptor retinoid-binding protein (IRBP). All dogs with tumors displaying histological and immunohistochemical features of retinal differentiation were ≤2 years of age. All tumors diagnosed as medulloepitheliomas (n = 4) did not display histological and immunohistochemical features of retinal differentiation and were present in dogs 7 years or older. Age of onset, in conjunction with immunohistochemistry for opsin, S-Ag, and IRBP, is an important aid in the differentiation of primary, primitive neuroectodermal tumors arising within the canine ciliary body, retina, and optic papilla.

Malignant transformation of a putative eyelid papilloma to squamous cell carcinoma in a dog.

A 6-year-old female spayed Chihuahua was presented for the evaluation of generalized pigmented cutaneous masses, one of which was present on the lower right eyelid. The dog was not on immunosuppressive medications and did not have historical or laboratory evidence of underlying endocrine disease, including hypothyroidism and hyperadrenocorticism. Histopathology, immunohistochemistry, and polymerase chain reaction of a cutaneous biopsy from the left antebrachium containing representative lesions confirmed viral papillomatosis. Additionally, histopathology of the antebrachial mass revealed regions of epithelial dysplasia suggestive of possible early transformation to malignancy. Over the course of 5 months, the mass on the right lower eyelid progressed to encompass and efface the majority of the eyelid margin. Additionally, the eyelid tumor had changed from an ovoid, brown pigmented mass to an irregular, flesh-colored mass. At the dog's last recheck examination, a corneal ulcer had developed beneath the irregular dorsal margin of the tumor. Histopathology of the eyelid mass was consistent with squamous cell carcinoma (SCC) and was positive for the presence of papillomavirus using polymerase chain reaction. This report describes the transformation of a putative viral eyelid papilloma into a malignant SCC in an adult dog.

Localization of canine, feline, and mouse renal membrane proteins.

Immunohistochemistry allows the localization of proteins to specific regions of the nephron. This article reports the identification and localization of proteins in situ within normal canine, feline, and mouse kidney by immunohistochemistry; maps their distribution; and compares results to previously reported findings in other species. The proteins investigated are aquaporin 1, aquaporin 2, calbindin D-28k, glutathione S-transferase-α, and Tamm-Horsfall protein. Aquaporins are integral membrane proteins involved in water transport across cell membranes. Calbindin D-28k is involved in renal calcium metabolism. Glutathione S-transferase-α is a protein that aids in detoxification and drug metabolism. The role of Tamm-Horsfall protein is not fully understood. Proposed functions include inhibition of calcium crystallization and reduction of bacterial urinary tract infection. The authors' findings in the dog are similar to those in other species: Specifically, the authors localize aquaporin 1 to the proximal convoluted tubule epithelium, vasa recta endothelium, and descending thin limbs; aquaporin 2 to collecting duct epithelium; and calbindin D-28k within distal convoluted tubule epithelium. Glutathione S-transferase-α has variable expression and is found in only the renal transitional epithelium in some individuals, in only the proximal straight tubules in others, or in both locations in others. Tamm-Horsfall protein localizes to thick ascending limb epithelium. These findings are similar in the cat, with the exception that aquaporin 1 is located in glomerular podocytes, in addition to proximal convoluted tubule epithelium, and glutathione S-transferase-α is found solely within the proximal convoluted tubule within all kidney samples examined. The mouse kidney is almost identical to the dog but expresses glutathione S-transferase-α in the glomeruli only.

Neurolymphomatosis in a dog with B-cell lymphoma.

Lymphoma in the left femoral nerve of a 10-year-old English Cocker Spaniel caused complete paralysis of the affected limb. Neoplastic cells were immunopositive for CD79a and Pax5 and negative for CD3. Neoplastic cells were in multiple lymph nodes and one kidney but spared bone marrow. The clinical and histologic features in this case resemble those of the rare human condition of neurolymphomatosis.

Genomic landscapes of canine splenic angiosarcoma (hemangiosarcoma) contain extensive heterogeneity within and between patients.

Cancer genomic heterogeneity presents significant challenges for understanding oncogenic processes and for cancer's clinical management. Variation in driver mutation frequency between patients with the same tumor type as well as within an individual patients' cancer can shape the use of mutations as diagnostic, prognostic, and predictive biomarkers. We have characterized genomic heterogeneity between and within canine splenic hemangiosarcoma (HSA), a common naturally occurring cancer in pet dogs that is similar to human angiosarcoma (AS). HSA is a clinically, physiologically, and genomically complex canine cancer that may serve as a valuable model for understanding the origin and clinical impact of cancer heterogeneity. We conducted a prospective collection of 52 splenic masses from 43 dogs (27 HSA, 15 benign masses, and 1 stromal sarcoma) presenting for emergency care with hemoperitoneum secondary to a ruptured splenic mass. Multi-platform genomic analysis included matched tumor/normal targeted sequencing panel and exome sequencing. We found candidate somatic cancer driver mutations in 14/27 (52%) HSAs. Among recurrent candidate driver mutations, TP53 was most commonly mutated (30%) followed by PIK3CA (15%), AKT1 (11%), and CDKN2AIP (11%). We also identified significant intratumoral genomic heterogeneity, consistent with a branched evolution model, through multi-region exome sequencing of three distinct tumor regions from selected primary splenic tumors. These data provide new perspectives on the genomic landscape of this veterinary cancer and suggest a cross-species value for using HSA in pet dogs as a naturally occurring model of intratumoral heterogeneity.