The secondary KIT mutation p.Ala510Val in a cutaneous mast cell tumour carrying the activating mutation p.Asn508Ile confers resistance to masitinib in dogs.

BACKGROUND: Gain-of-function mutations in KIT are driver events of oncogenesis in mast cell tumours (MCTs) affecting companion animals. Somatic mutations of KIT determine the constitutive activation of the tyrosine kinase receptor leading to a worse prognosis and a shorter survival time than MCTs harbouring wild-type KIT. However, canine MCTs carrying KIT somatic mutations generally respond well to tyrosine kinase inhibitors; hence their presence represents a predictor of treatment effectiveness, and its detection allows implementing a stratified medical approach. Despite this, veterinary oncologists experience treatment failures, even with targeted therapies whose cause cannot be elucidated. The first case of an MCT-affected dog caused by a secondary mutation in the tyrosine kinase domain responsible for resistance has recently been reported. The knowledge of this and all the other mutations responsible for resistance would allow the effective bedside implementation of a deeply stratified and more effective medical approach. CASE PRESENTATION: The second case of a canine MCT carrying a different resistance mutation is herein described. The case was characterised by aggressive behaviour and early metastasis unresponsive to both vinblastine- and masitinib-based treatments. Molecular profiling of the tumoural masses revealed two different mutations; other than the already known activating mutation p.Asn508Ile in KIT exon 9, which is tyrosine kinase inhibitor-sensitive, a nearly adjacent secondary missense mutation, p.Ala510Val, which had never before been described, was detected. In vitro transfection experiments showed that the secondary mutation did not cause the constitutive activation by itself but played a role in conferring resistance to masitinib. CONCLUSIONS: This study highlighted the importance of the accurate molecular profiling of an MCT in order to improve understanding of the molecular mechanism underlying tumourigenesis and reveal chemoresistance in MCTs for more effective therapies. The detection of the somatic mutations responsible for resistance should be included in the molecular screening of MCTs, and a systematic analysis of all the cases characterised by unexpected refractoriness to therapies should be investigated in depth at both the genetic and the phenotypic level.

Ultrasonographic characteristics of the abdominal esophagus and cardia in dogs.

Differential diagnoses for regurgitation and vomiting in dogs include diseases of the gastroesophageal junction. The purpose of this cross-sectional study was to describe ultrasonographic characteristics of the abdominal esophagus and gastric cardia in normal dogs and dogs with clinical disease involving this region. A total of 126 dogs with no clinical signs of gastrointestinal disease and six dogs with clinical diseases involving the gastroesophageal junction were included. For seven euthanized dogs, ultrasonographic features were also compared with gross pathology and histopathology. Cardial and abdominal esophageal wall thicknesses were measured ultrasonographically for all normal dogs and effects of weight, sex, age, and stomach filling were tested. Five layers could be identified in normal esophageal and cardial walls. The inner esophageal layer was echogenic, corresponding to the cornified mucosa and glandular portion of the submucosa. The cardia was characterized by a thick muscularis, and a transitional zone between echogenic esophageal and hypoechoic gastric mucosal layers. Mean (±SD) cardial wall thicknesses for normal dogs were 7.6 mm (±1.6), 9.7 mm (±1.8), 10.8 mm (±1.6), 13.3 mm (±2.5) for dogs in the <10 kg, 10-19.9 kg, 20-29.9 kg and ≥30 kg weight groups, respectively. Mean (±SD) esophageal wall thicknesses were: 4.1 mm (±0.6), 5.1 mm (±1.3), 5.6 mm (±1), and 6.4 mm (±1.1) for the same weight groups, respectively. Measurements of wall thickness were significantly correlated with dog weight group. Ultrasonography assisted diagnosis in all six clinically affected dogs. Findings supported the use of transabdominal ultrasonography as a diagnostic test for dogs with suspected gastroesophageal disease.

A case of well-differentiated palpebral liposarcoma in a Guinea pig (Cavia porcellus).

Liposarcomas are rare malignant tumors of the adipose tissue which are well described in humans and animals. Wide margin excision is the recommended treatment for these infiltrative, slow to metastasize tumors. Primary liposarcoma with ocular localization is a very rare tumor in humans, dogs and cats. This report describes, for the first time, a palpebral liposarcoma in a 18-month old guinea pig that presented with a large palpebral mass and purulent discharge in the right eye. The ophthalmic evaluation revealed a one-centimeter infiltrating subcutaneous mass within the upper eyelid, a severe chemosis and hyperhemia of the palpebral and bulbar conjunctiva of the right eye. Cytologic examination of the mass revealed only epithelial cells. Histologic examination interpreted the lesion as a xanthogranulomatous reaction possibly secondary to meibomian gland rupture or inflammation. One month later, the mass had increased in size and the animal had stopped eating. Euthanasia was performed and a large biopsy was submitted for another histological examination. Histopathology revealed polygonal to rounded cells with a large, empty intracytoplasmic vacuole, and an ovoid, eccentrically located nucleus. The histology was consistent with a well-differentiated liposarcoma. Given the unusual location, immunohistochemistry was performed to ascertain the mesenchymal nature of the neoplasm.

Spinal epidural and synovial lipomatosis in a 3-year-old Eurasian dog receiving sustained steroid therapy.

This report describes a spinal cord epidural and synovial lipomatosis in a 3-year-old neutered male Eurasian dog. This dog presented for ambulatory paraparesis and was previously treated with immunosuppressive dosages of prednisolone for 2 years. Computed tomography (CT) myelography and magnetic resonnance imaging (MRI) images identified dorsal compression of the thoraco-lumbar spinal cord by hypertrophic epidural fat. Histological examination identified extensive well-differentiated mature adipose tissue in the subepithelial area of the tarsal synovium. Prednisolone is a reported predisposing factor in humans with lipomatosis.

Association of gastric lymphofollicular hyperplasia with Helicobacter-like organisms in dogs.

BACKGROUND: The relationships among gastric lymphoid follicular hyperplasia (GLFH), Helicobacter-like organisms (HLOs), and clinical signs have not been established in dogs. OBJECTIVES: To evaluate the epidemiologic, clinical, endoscopic, and histopathologic findings associated with GLFH in dogs, and determine the association of GLFH with HLOs and the French Bulldog (FB) breed. ANIMALS: Two hundred eighty-eight dogs that underwent gastroscopy between 2013 and 2016. METHODS: Retrospective, cross-sectional study. Gastric biopsy samples were reviewed and scored for inflammation and HLOs. Dogs were divided into 3 groups: group 1 (63 FBs), group 2 (45 non-FB brachycephalic dogs), and group 3 (180 nonbrachycephalic dogs). Variables were evaluated for their association with GLFH. RESULTS: Univariate analysis determined that intact males, young age, vomiting, gastroscopic findings (discoloration, hemorrhage, and ulcers), and histopathologic findings (gastric lamina propria lymphocytic infiltration and HLO score) were associated with GLFH (P ≤ .03). In the multivariate analysis, GLFH was associated with the HLO score (odds ratio [OR] > 5 for HLO scores 1-2 and >15 for HLO score of 3; P < .001), with vomiting (OR > 4; P = .01) but not with FB breed (P = .76) and age (P = .1). The HLO score was associated with younger age (P < .001). CONCLUSION AND CLINICAL IMPORTANCE: The HLO score was associated with a high GLFH score. Vomiting was associated with GLFH. Helicobacter-like organisms are highly prevalent in young dogs and GLFH is indirectly associated with this factor. Clinical relevance of the identification of GLFH and HLO remains to be determined.

Canine copper-associated hepatitis: A retrospective study of 17 clinical cases.

Background: Copper-associated hepatitis (CAH) is a well-documented chronic hepatic disease in dogs. In some breeds, the disease results from an inherited defect in copper metabolism. In others, it is unclear whether its acummulation is a primary or secondary condition. Reports of copper accumulation in dog breeds that are not genetically predisposed are increasing. Aim: To describe the epidemiology, clinical and laboratory findings, liver biopsy techniques, and treatment response in dogs with CAH. Methods: A retrospective study was performed, drawing upon medical records from CAH dogs at a Veterinary Referral Hospital in Paris, France. The diagnosis of CAH had been confirmed in these patients by positive rhodanine staining of hepatic tissue obtained through biopsy. Medical records were mined for the following data: age at presentation, sex, breed, chief presenting complaints, abdominal ultrasound (US) findings, and rhodanine staining pattern. Results: A total of 17 dogs were included in the study. Median age at presentation was 8-year old (4-11). No sex predisposition was found. Terriers (4/17) and German Shepherd Dogs (GSD, 3/17) were overrepresented. American Staffordshire Terriers and Beauceron had not previously appeared in case reports on CAH; two of each breed were identified in this study. Clinical signs of affected dogs were non-specific. An incidental identification of increased liver-enzymes was observed in 5/17 dogs. A heterogeneous, mottled liver was frequently described (5/17) on abdominal US. Liver biopsies were performed by US-guided percutaneous approach in 10/17 dogs, laparoscopy and laparotomy in 6/17 and 1/17, respectively. The rhodanine staining pattern was centrilobular (zone 3) in 8/17 dogs and periportal (zone 1) in 3/17 dogs. The pattern was considered multifocal in 6/17 dogs. Conclusion: Increased liver enzymes may be the only clinical finding in dogs with copper-associated hepatitis, reflecting the silent progression of this disease. Centrilobular pattern of rhodanine staining was observed in the majority of cases suggesting the primary condition of the disease. Results of this study are consistent with the current literature, which reports that terriers and GSD are predisposed to CAH. This is the first description of CAH in Beauceron and American Staffordshire Terrier dogs.

Osteomyelitis and discospondylitis due to Scedosporium apiospermum in a dog.

A 6-year-old, 30-kg, female German Shepherd Dog, living in a leishmaniasis enzootic area, was presented with a severe rear limb motor disorder and a medical history of acute onset of fever. Routine hematology indicated neutrophilia. Spinal survey radiographs were consistent with osteomyelitis and discospondylitis. Because of the poor clinical prognosis and the painful nature of the lesions, the dog was euthanized at the owners' request. At necropsy, T13-L1 vertebrae had large areas of necrosis within the vertebral bodies. Histopathological findings were consistent with chronic, severe, fungal osteomyelitis and discospondylitis. Polymerase chain reaction identified Scedosporium apiospermum, a eutrophic filamentous fungus now recognized as an emerging agent of severe infections in immunosuppressed human patients.

Immunohistochemical characterization of a hepatic neuroendocrine carcinoma in a cat.

A hepatic mass was identified in a 5-year-old, female mixed-breed cat that died spontaneously after a clinical history of progressive emaciation, ptyalism, and persistent coryza. At necropsy, a 7-cm-diameter, yellow-brown, firm, multilobulated tumor was identified in the liver. Microscopically, the mass consisted of neoplastic cells arranged in small, closely packed nests within a thin fibrovascular stroma. These cells were of medium sized and polygonal, with fine argyrophilic cytoplasmic granules. Nuclei were predominantly round with finely stippled chromatin and indistinct nucleoli. Mitotic figures were numerous. Immunohistochemically, most of the neoplastic cells were immunoreactive for chromogranin A, neuron-specific enolase (NSE), and cytokeratin AE1/AE3 and weakly labeled for synaptophysin. The tumor was negative for glial fibrillary acidic protein (GFAP), vimentin, and cytokeratins 5, 6, 8, and 17. Vascular emboli and intrahepatic micrometastasis were also identified with chromogranin A. All these features were consistent with a hepatic neuroendocrine carcinoma and emphasized the importance of using a panel of antibodies to diagnose such rare tumors.

Presence of neural progenitors in spontaneous canine gliomas: A histopathological and immunohistochemical study of 20 cases.

Gliomas are the most common primary brain tumours in humans and are associated with a poor prognosis. An accurate animal model of human glioma tumorigenesis is needed to test new treatment strategies. Dogs represent a promising model because they develop spontaneous diffusely-infiltrating gliomas. This study investigated whether spontaneous canine gliomas contain cancer stem cells previously identified in all grades of human gliomas. Twenty spontaneous cases of canine gliomas were graded according to the human WHO classification. The expression of different markers of lineage differentiation was evaluated with immunohistochemistry as follows: nestin and CD133 for neural stem cells, doublecortin for neuronal progenitor cells, Olig2 for glial progenitor cells, glial fibrillary acidic protein, vimentin and S-100 for mature glial cells, and NeuN and ßIII-tubulin for mature neurons. Gliomas were characterised as follows: five grade II (oligodendrogliomas); nine grade III (seven anaplastic oligodendrogliomas, one anaplastic astrocytoma, one anaplastic oligoastrocytoma); six grade IV (glioblastomas). Immunohistochemical evaluation revealed that (1) nestin and CD133 were expressed in all grades of gliomas with a higher proportion of positive cells in high-grade gliomas; (2) the expression of S-100 protein and Olig2 did not differ substantially between astrocytic and oligodendroglial tumours, and (3) all gliomas were negative for mature neuron markers. The results demonstrated the presence of undifferentiated neural progenitors in all grades of spontaneous canine gliomas, confirming the relevance of this animal model for further studies on cancer stem cells.