Canine chemodectoma (extra-adrenal paragangliomas)--a comparative study

A case of neoplastic synchronism in a dog

INTRODUCTION

Synchronous primary tumors are considered severe, comorbid conditions in people representing neoplasm that develop independently and concomitantly. A diagnosis of synchronous tumors was made in a dog, underlying the difficulties to reach it without the aid of multiple diagnostic techniques aimed to demonstrate the simultaneous coexistence of different tumor types.

MATERIALS AND METHODS

A 7-year-old male Boxer dog presented several tumors located on the skin of the left hind limb and the scrotal region. Moreover, additional tumors in the testicles, after palpation and ultrasound examination, were detected. Following diagnostic results, the cutaneous tumor, scrotum, and testes were surgically removed.

RESULTS

Pathological investigations revealed the presence of five different tumors: a cutaneous mast cell tumor; a scrotal melanocytoma; three testicular neoplasms (Sertoli Sustentacular cell tumor, seminoma, and interstitial Leydig cell tumor).

CONCLUSIONS

The present report describes a neoplastic synchronism due to the presence of five different primary tumors in a dog and, for the first time the presence of a collision testicular tumor together with other non-testicular primary tumors. The occasional finding underlines the importance of the knowledge of such conditions in the process of decision-making and in carrying out all the proper diagnostic procedures for a correct diagnosis and clinical staging.

Intracardiac malignant nonchromaffin paraganglioma (chemodectoma) in a cat

A 5-year-old male castrated Domestic Shorthair cat was presented to a veterinary specialty hospital for evaluation of large-volume pleural effusion. Echocardiography revealed a large intracardiac mass at the level of the interatrial septum impairing right atrial inflow resulting in lymphocytic pleural effusion and ascites. Differential diagnoses included lymphoma, hemangiosarcoma, rhabdomyosarcoma, chemodectoma, neurofibrosarcoma, myxoma, metastatic carcinoma or intracardiac thrombus, abscess or granuloma. Due to poor long-term prognosis and recurrent, large-volume pleural effusion, the cat was humanely euthanized. The heart was submitted for histopathologic evaluation. The mass was subsequently determined to be a malignant extra-adrenal nonchromaffin paraganglioma (chemodectoma) arising from the pulmonary trunk near its bifurcation in the region of the glomus pulmonale. Chemodectomas are rare in cats and to the authors' knowledge, there are no reports of one originating from the glomus pulmonale.

Choroidal neuroendocrine neoplasia in a dog

OBJECTIVE

To report onset and progression of clinical signs of a neuroendocrine neoplasm (NEN) presumed metastatic to the choroid in a dog.

ANIMALS STUDIED

A 7.5-year-old female spayed German shepherd dog mix referred for advanced imaging and evaluation of a subretinal mass in the right eye.

PROCEDURES

Procedures performed included general physical and ophthalmic examinations; ocular, orbital, and abdominal ultrasonography; thoracic radiographs; cranial magnetic resonance imaging; serologic testing for infectious agents; analysis of hematologic as well as serum and urine biochemical parameters; echocardiography; electrocardiography; cytologic assessment of lymph nodes; and histopathology and immunohistochemistry of the enucleated globe.

RESULTS

Examination and imaging identified a pigmented mass within and expanding the superior choroid. Following enucleation, a choroidal NEN with tumor emboli in scleral blood vessels was diagnosed by histopathologic assessment and confirmed by immunohistochemical labelling. Despite extensive and repeated diagnostic testing over many months, a putative primary site was not identified until 19 months after the initial ocular signs were noted. At that time, a heart-base mass and congestive heart failure were highly suggestive of a chemodectoma.

CONCLUSION

This comprehensive report of a NEN presumed metastatic to the choroid in a dog suggests that ocular disease can be a very early and solitary sign of NEN in the dog.

A Multi-Institutional Retrospective Analysis of Toceranib Phosphate for Presumed or Confirmed Canine Aortic Body Chemodectomas

Aortic body tumors, specifically chemodectomas, are the second most common type of canine cardiac tumor; however, information about treatment is currently lacking. This study included dogs with a presumptive or definitive diagnosis of an aortic body chemodectoma that underwent treatment with toceranib phosphate. Cases were solicited via the American College of Veterinary Internal Medicine Cardiology, Internal Medicine, and Oncology listservs using an electronic survey. Cox multivariate analysis of factors potentially impacting survival time was completed. Twenty-seven (27) cases were included in analysis. The clinical benefit rate (complete remission, partial remission, or stable disease >10 weeks) was 89%. A median survival time of 478 days was found for those receiving toceranib alone (n = 14), which was not statistically different from those treated with additional modalities (521 days). No factors evaluated statistically impacted outcome. Further, prospective studies are warranted to evaluate the use of toceranib for the treatment of canine aortic body chemodectomas.

Long-term outcomes with conventional fractionated and stereotactic radiotherapy for suspected heart-base tumours in dogs

Published radiotherapy results for suspected heart-based tumours in dogs are limited. In this retrospective longitudinal study (3/2014-2019), eight dogs with either clinical signs attributable to a heart-base mass (6), or asymptomatic with a progressively larger mass on echocardiogram (2), received conventional fractionated radiotherapy (CFRT) or stereotactic body radiotherapy (SBRT). Clinical findings in symptomatic cases included one or more of the following: retching/coughing (4), exercise intolerance (2), collapse (1), pericardial effusion (2), rare ventricular premature contractions (2), abdominal effusion (1), or respiratory distress due to chylothorax (1). CFRT cases received 50 Gray (Gy) in 20 fractions and SBRT cases received 30 Gy in 5 or 24 Gy in three fractions. Two dogs received chemotherapy post-radiation. At analysis, 7/8 dogs were deceased and one was alive 684 days post-treatment. The estimated median overall survival (MOS) from first treatment was 785 days (95% CI 114-868 days, [range 114-1492 days]). Five dogs received CFRT (MOS 817 days; (95% CI 155 days-not reached [range 155-1492 days])). Three dogs received SBRT with one alive at analysis (MOS 414 days, (95% CI, 114 days-not reached [range 114-414 days])). No statistically significant difference was found between survival for CFRT and SBRT. Of the symptomatic patients, 5/6 showed improvement. Mass size reduced in 4/5 cases receiving follow-up ultrasounds. Possible complications included asymptomatic radiation pneumonitis (4), atrial tachycardia/premature beats (4) and pericardial effusion with heart failure coincident with tumour progression (1). This study provides preliminary evidence that radiotherapy may impact clinically relevant or progressively enlarging heart-base masses.

A retrospective analysis of stereotactic body radiation therapy for canine heart base tumors: 26 cases

INTRODUCTION

This study retrospectively evaluated outcomes and adverse radiation effects (AREs) associated with stereotactic body radiation therapy (SBRT) for canine heart base tumors (HBTs). A secondary aim was to identify any demographic or echocardiographic factors that might determine which dogs would most benefit from SBRT.

ANIMALS

Twenty-six dogs that received SBRT for an imaging-based diagnosis of a HBT were evaluated.

METHODS

Twenty-three dogs were treated with three fractions of 10 Gy delivered daily or every other day. The remaining 3 dogs received variable protocols of one to five fractions. Demographic, echocardiographic, and radiographic information, AREs, and treatment responses were collected. Correlations of these data with survival time were evaluated.

RESULTS

The median overall survival time was 404 days (95% confidence interval: 239-554 days). The majority of dogs experienced a partial response (25%) or stable disease (60%) for a median duration of 333 days (95% confidence interval: 94-526 days). Three dogs had progressive disease within six months of SBRT. Radiographic pneumonitis was identified in 7 of 23 dogs, and clinical pneumonitis was identified in 4 dogs. No other AREs were noted. The rate of distant metastasis was 13%. On multivariate analysis, it was found that vena caval obstruction, supraventricular and ventricular arrhythmias, clinical signs, and enlarged locoregional lymph nodes at presentation were negatively associated with survival time.

CONCLUSIONS

Stereotactic body radiation therapy was delivered with a low rate and degree of normal tissue complications. Asymptomatic dogs with confirmed, progressive growth of a HBT may most likely benefit from SBRT.

Pericardial Patch as a Palliative Treatment in Three Dogs Affected by Unresectable Cardiac Tumor

This report is aimed at describing a pericardial patch for unresectable cardiac tumors as a palliative technique to prevent pleural effusion.

Each dog underwent the same diagnostic protocol including a cardiological assessment, hematology and biochemistry profile, urinary test, abdominal and heart ultrasonography and chest radiographs. Computed tomography was always performed in order to exclude any potential metastatic lesions. All dogs underwent open pericardiectomy: the pericardium was opened and transposed on the mass according to its shape. Biopsy of the mass was always performed. Histopathological evaluation of the masses described two HAS and one chemodectoma. Chemotherapy protocol includes doxorubicin that was weekly administered. Dogs with HSA survived 65 and 85 days respectively without pleural effusion, while the dog with chemodectoma died after six months for reasons unrelated to the tumor.

No evidence of pleural effusion was observed during the heart recheck, monthly performed.

Pericardial patch is a potential choice as a palliative treatment for unresectable cardiac tumors. No pleural effusion was seen in three dogs affected by unresectable cardiac tumors.

Sensitivity, specificity, and interobserver variability of survey thoracic radiography for the detection of heart base masses in dogs

OBJECTIVE To determine the sensitivity, specificity, and interobserver variability of survey thoracic radiography (STR) for the detection of heart base masses (HBMs) in dogs. DESIGN Retrospective case-control study. ANIMALS 30 dogs with an HBM and 120 breed-matched control dogs (60 healthy dogs and 60 dogs with heart disease and no HBM). PROCEDURES In a blinded manner, 2 observers (designated as A and B) evaluated STR views from each dog for a mass-like opacity cranial to the heart, tracheal deviation, cardiomegaly, findings suggestive of pericardial effusion or right-sided congestive heart failure, and soft tissue opacities suggestive of pulmonary metastases. Investigators subsequently provided a final interpretation of each dog's HBM status (definitely affected, equivocal, or definitely not affected). RESULTS Considering equivocal interpretation as negative or positive for an HBM, the sensitivity of STR for diagnosis of an HBM was 40.0% (95% confidence interval [CI], 22.5% to 57.5%) and 56.7% (95% CI, 38.9% to 74.4%), respectively, for observer A and 63% (95% CI, 46.1% to 80.6%) and 80.0% (95% CI, 65.7% to 94.3%), respectively, for observer B. The corresponding specificity was 96.7% (95% CI, 93.5% to 99.9%) and 92.5% (95% CI, 87.8% to 97.2%), respectively, for observer A and 99.2% (95% CI, 97.5% to 100%) and 92.5% (95% CI, 87.8% to 97.2%), respectively, for observer B. The presence of a mass-like opacity cranial to the heart or tracheal deviation, or both, was significantly associated with a true diagnosis of HBM. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that STR is a highly specific but not a highly sensitive predictor of HBM in dogs.

Pathologic and Immunohistochemical Findings in a Feline Aortic Body Tumor

The presence of a heart-base tumor was diagnosed by ultrasound imaging in a 10-year-old, female, domestic shorthaired cat presenting with dyspnea and pleural effusion because of the presence of a modified transudate. Hematology and clinical chemistry were unremarkable. The owner elected euthanasia. At necropsy, a locally extensive, firm, multilobulated nodule surrounded the pulmonary vein. The tumor was composed of lobules of large polygonal cells separated by a fine fibrovascular stroma. Tumor cells infiltrated the myocardium, and neoplastic emboli were present, but no metastases were macroscopically detectable. Tumor cells were immunohistochemically positive for chromogranin A, for synaptophysin and, faintly, for neuron-specific enolase and negative for vimentin, cytokeratin, a smooth muscle actin, glial fibrillary acidic protein, thyreoglobulin, and calcitonin. Based on histologic and immunohistochemical findings, the diagnosis of chemodectoma was made.

Trends in popularity of some morphological traits of purebred dogs in Australia

BACKGROUND

The morphology of dogs can provide information about their predisposition to some disorders. For example, larger breeds are predisposed to hip dysplasia and many neoplastic diseases. Therefore, longitudinal trends in popularity of dog morphology can reveal potential disease pervasiveness in the future. There have been reports on the popularity of particular breeds and behavioural traits but trends in the morphological traits of preferred breeds have not been studied.

METHODS

This study investigated trends in the height, dog size and head shape (cephalic index) of Australian purebred dogs. One hundred eighty-one breeds derived from Australian National Kennel Council (ANKC) registration statistics from 1986 to 2013 were analysed. Weighted regression analyses were conducted to examine trends in the traits by using them as outcome variables, with year as the explanatory variable and numbers of registered dogs as weights. Linear regression investigated dog height and cephalic index (skull width/skull length), and multinomial logistic regression studied dog size.

RESULTS

The total number of ANKC registration had decreased gradually from 95,792 in 1986 to 66,902 in 2013. Both weighted minimal height (p = 0.014) and weighted maximal height (p < 0.001) decreased significantly over time, and the weighted cephalic index increased significantly (p < 0.001). The odds of registration of medium and small breeds increased by 5.3 % and 4.2 %, respectively, relative to large breeds (p < 0.001) and by 12.1 % and 11.0 %, respectively, relative to giant breeds (p < 0.001) for each 5-year block of time.

CONCLUSIONS

Compared to taller and larger breeds, shorter and smaller breeds have become relatively popular over time. Mean cephalic index has increased, which indicates that Australians have gradually favoured breeds with shorter and wider heads (brachycephalic). These significant trends indicate that the dog morphological traits reported here may potentially influence how people select companion dogs in Australia and provide valuable predictive information on the pervasiveness of diseases in dogs.

Histopathological and immunohistochemical evaluation of malignant potential in canine aortic body tumours

In order to verify the malignant potential of aortic body tumours (ABTs) in dogs, 13 cases of canine ABT were studied histopathologically and immunohistochemically. The cases were divided into two groups according to the presence or absence of metastases to other organs at necropsy examination (metastasis group [n = 9] and non-metastasis group [n = 4]). The mean tumour weight:body weight ratio (TW:BW; g/kg) in the metastasis group (9.3 ± 6.7) was significantly higher than that in the non-metastasis group (1.5 ± 1.7) (P <0.05). In both groups, the neoplastic cells had malignant features including pleomorphism, anisocytosis and anisokaryosis, and mononuclear giant cells were present, showing invasion through the capsule and into the vascular lumen and other adjacent tissues. The mitotic index (MI), mean nuclear area (NA) for size value and coefficient of variation of the nuclear area (CVNA) for anisonucleosis did not differ significantly between the two groups. These findings show that anaplastic characteristics are present regardless of the tumour size or the presence or absence of metastases, suggesting that these tumours are generally malignant or potentially malignant. Immunohistochemical analysis using neuroendocrine markers including neuron-specific enolase, chromogranin A and S100 revealed no obvious differences in labelling intensity of neoplastic cells related to the presence or absence of metastases or associated with the mean TW:BW, MI, NA or CVNA value, indicating that immunohistochemistry has no practical value for determining the tumour grade of canine ABTs.

Prevalência e aspectos anatomopatológicos das neoplasias primárias do coração, de tecidos da base do coração e metastáticas, em cães do Sul de Minas Gerais (1994-2009)

Este estudo teve como objetivo determinar a prevalência e achados anatomopatológicos de tumores primários e metastáticos do coração ou de tecidos da base do coração, diagnosticados em caninos do Sul de Minas Gerais. O diagnóstico foi realizado mediante análise histopatológica e imuno-histoquímica das neoplasias. Durante os anos de 1994-2009, foram realizadas 2397 necropsias em caninos. Neoplasias no coração foram detectadas em 31 cães (1,29%), onde, sete (22,58%) eram primárias e 24 (77,42%) metastáticas. As neoplasias diagnosticadas como primárias do coração foram o hemangiossarcoma (1/7) e o mixoma (1/7); e como primárias da base do coração o quimiodectoma (3/7) e o carcinoma de tireoide ectópica (2/7). A frequência foi maior em cães machos (5/7), da raça Boxer (3/7) e com idade média de 9,7±1,88 anos. Nas neoplasias metastáticas, a frequência foi maior em fêmeas (15/24), em cães da raça Rottweiler (7/24) e a idade média foi de 7,5±3,23 anos, sendo o linfoma de células T a neoplasia metastática de maior ocorrência (7/27).

A case of synchronous hepatocellular carcinoma and aortic body chemodectoma in a dog - pathological case report

The authors describe a case of synchronously occurring (double) tumours, i.e. primary hepatocellular carcinoma and aortic body chemodectoma in a 14-year-old mixed-breed male dog. The tumours were identified during necropsy, following euthanasia. In the last months of its life, the dog showed signs of weakness, anorexia, apathy, inactivity, and abdominal palpation elicited a painful reaction. The primary liver cancer emerged in the left lateral lobe without evidence of any distant metastases. Histopathological and immunohistochemical investigations revealed a well-differentiated, trabecular, claudin-7-, claudin-5- and pancytokeratin-negative hepatocellular carcinoma. The Ki-67 proliferation index was 33%. During necropsy, a synchronously occurring benign, grade I type aortic body chemodectoma was also detected in the dog. This neuroendocrine tumour showed chromogranin-, synaptophysin-, neuron-specific enolase- and S100 protein-positivity, and the Ki-67 proliferation index was 2%. The authors believe that this is the first description of synchronously occurring hepatocellular carcinoma and aortic body chemodectoma in a dog.

Simultaneous aortic body tumor and pulmonary histiocytic sarcoma in a flat-coated retriever

A case of multiple primary tumors observed in the heart base and in the lung of a 7-year-old intact female, flat-coated retriever was reported. Morphological differences between both tumors and detailed immunohistochemical study revealed that the cardiac neoplasm was as a malignant aortic body tumor and the lung tumor was a pulmonary histiocytic sarcoma. The occurrence of aortic body tumor with other primary neoplasms has been previously reported in animals suggesting that this might be a common presentation in dogs.

Aortic body chemodectoma causing pulmonary oedema in a cat

A seven-year-old male domestic shorthaired cat was presented with persistent dyspnoea. Thoracic radiography and echocardiography revealed pulmonary oedema and a mass at the base of the heart. At necropsy the mass was found to be an aortic body chemodectoma that had metastasised to the sternal lymph node. This is a rare tumour in the cat, the third reported case where there was evidence of metastasis, and only the second reported case where there was evidence of lymphocytic infiltration of the primary tumour. Pulmonary oedema is an unusual presentation of this tumour in the cat.

Multiple endocrine neoplasia in a dog

Multiple endocrine neoplasms, including an insulinoma, bilateral adrenocortical adenocarcinomas and an aortic paraganglioma, were diagnosed after euthanasia in a 12-year-old spayed female dog of mixed breed with a history of progressive anorexia, vomiting, diarrhoea, weight loss, polyuria and polydipsia, regenerative anaemia and hypoglycaemia. The clinical, gross pathological, microscopical, immunohistochemical and ultrastructural findings were consistent with the human syndrome of multiple endocrine neoplasia.

Intrapericardial neoplasia in dogs

A retrospective study was conducted from 1,919 necropsies of dogs, and 52 cases were selected on the basis of primary or metastatic neoplasia in the pericardium, the heart base, or the myocardium. Primary intrapericardial neoplasms were more frequent than intrapericardial metastases. Hemangiosarcomas were the most frequent primary neoplasms, followed by chemodectomas. Lymphomas were the most frequent metastatic neoplasms, followed by fibrosarcomas and rhabdomyosarcomas. Other neoplasms, either primary or metastatic, occurred rarely.

Malignant aortic body tumor in a Holstein cow

A malignant aortic body tumor was observed in a 5-year-old female Holstein cow. The neoplastic mass, of 22 x 17 x 15 cm in size, was located at the base of the left atrium, having irregular lobular structures. The tumor cells had slightly eosinophilic cytoplasm, and a round or oval nucleus. Metastasis was only present in the premediastinal lymph node. The tumor cells exhibited intense immunoreactivity for neuron-specific enolase (NSE) and synaptophysin, and were moderately positive for chromogranin A. Electronmicroscopy revealed membrane-limited granules in the cytoplasm. The cultured cells were spindle in shape, and having projectional cytoplasm. They were intensely positive for NSE, synaptophysin, chromogranin A, and neurofilament (200 kD). Consequently, this case was diagnosed as a malignant aortic body tumor from the neuroecrodermal origin.

Systemic, metastatic, eu- and heterotope tumours of the heart in necropsied dogs

10,090 dissections of dogs exhibited 2631 neoplastic processes of which 309 involved the heart in the form of eu- and heteropic tumours. The most common primary and/or secondary heart tumour type was hemangiosarcoma (n = 187), followed by paraganglioma (n = 46), carcinoma (n = 33), malignant lymphoma (n = 12), thyroid heart base tumour (n = 9), melanoma (n = 7), mast cell tumour (n = 3) and blastoma (n = 2). The tumour diagnoses were immunohistochemically proved by various antibodies to cytokeratins, vimentin, GFAP, NSE, von Willebrand factor, CD3, CD45RA, S100, thyroglobulin as well as histochemically with argyrophilic, Fontana-Masson and heterochromatic reactions. The odds ratio (OR) for breed and tumour prevalences were determined: German shepherds showed the highest OR for hemangiosarcomas and boxers for paragangliomas.

Posterior mediastinal paraganglioma involving the spinal cord of a dog

A posterior mediastinal paraganglioma is described in a five-year-old female collie showing paralysis of the hindlimbs. The mass was observed radiographically and a myelogram confirmed a spinal cord compression at the thoracic level. Histological examination of the mass diagnoses a paraganglioma which was confirmed by histochemical and immunohistochemical studies. This is compared with paraganglioma found in man.

Oncologic surgical emergencies

Surgical oncologic emergencies are relatively common and pose a clinical and therapeutic challenge for the emergency clinician. This article provides a clear clinical reference for assessment and management of some common surgical emergencies in cancer patients.

Metastasizing extra-adrenal paraganglioma with neurological signs in four dogs

Extra-adrenal paragangliomas associated with vertebral pain and clinical neurological abnormalities as a result of metastasis to the vertebral column were diagnosed in four dogs of different breeds by light microscopy. All were males (two intact and two neutered) aged 8 years. Metastatic neoplasms occurred as extradural masses with associated bone lysis at vertebrae C4 (2 cases), T12-L1 (1 case) and L4 (1 case). The neoplastic cells exhibited similar morphology with little variation between cases. All neoplasms showed cytoplasmic granules after staining with the Churukian-Schenk modification of the Pascual argyrophil stain for neurosecretory granules or for membrane bound electron-dense granules (dense-core granules). On immunohistochemical examination the neoplastic cells gave positive results for neuron-specific enolase and negative results for chromogranin and epithelial membrane antigen. Multiple organ metastasis and metastasis to bone have been reported previously, but these cases were unusual due to the involvement of the spine as an apparent predilection site for metastasis, and the sex (male) and age of the animals affected.

Carotid body tumors in the dog. Eleven cases (1978-1988)

Case records of 11 dogs with histologically confirmed carotid body tumors were reviewed. Surgical excision had been attempted in ten dogs with carotid body tumors, and one dog had been euthanatized at diagnosis. There were no intraoperative deaths but perioperative mortality was 40%. Horner's syndrome and laryngeal paralysis were the most common postoperative morbidities. The median survival time after surgery alone in the four dogs that survived the perioperative period was 25.5 months (range, 12-45 months). Two dogs treated with postoperative radiation therapy had survival times of 6 and 27 months. Of the six dogs surviving the perioperative period, two dogs are still alive at 19 and 32 months postoperatively. Of the four dogs that died, one was euthanatized 12 months postoperatively for nontumor-related causes. The remaining three dogs died of distant metastases. The carotid body tumors studied were characterized by local tissue invasion, neurovascular complications after therapy, and a propensity to metastasize to multiple sites in the body.

Neoplastic diseases of the thorax

Thoracic neoplasia comprises a heterogeneous group of diseases, many of which are distinctly uncommon in veterinary medicine. These diseases often present the clinician with diagnostic and therapeutic challenges. Careful diagnostic work-up and staging are essential for consideration of therapeutic options and formulation of prognosis. Neoplastic diseases of the thorax are classified here as tracheal tumors, primary lung tumors, nonrespiratory intrathoracic tumors, and thoracic wall tumors.

Carotid body tumor: an incidental finding in older ranch mink

Carotid body tumors were found incidentally at necropsy in 15 ranch mink (Mustela vision), mostly royal pastels, kept for studies on slow viral diseases. The mink, five males and ten females, were 77 to 135 months old (mean age 107 months). Loosely or firmly attached at the bifurcation of the common carotid artery, and 11 larger tumors were smooth-surfaced, discrete, pale brown, globoid masses that varied from 2.5 to 16 mm in diameter. Four tumors of microscopic size occurred in otherwise normal-looking carotid bodies. All were composed of densely packed polygonal cells disposed in sheets and cords or arranged in clusters by a reticulin meshwork rich in blood vessels. Always unilateral, the tumors had not invaded locally or metastasized. As seen in the smallest tumors, the neoplastic cells usually arose centrally in the carotid body and formed an expansive growth that replaced much of the normal parenchyma without necessarily enlarging the organ beyond normal limits. The cause of the tumors was not apparent. All tumor-bearing mink had lived at an elevation of 1,100 meters, and none had suffered from any obvious chronic cardiopulmonary disease.

Ectopic thyroid carcinoma with metastases in a beagle dog

A 10.25-year-old female beagle had an invasive neoplasm at the base of the heart which metastasized to the lungs, pancreas, and kidney. The neoplasm in these locations was composed of clusters of polyhedral cells surrounded by fine fibrovascular stroma. The differential diagnoses were malignant chemodectoma, ectopic parathyroid carcinoma, and ectopic thyroid carcinoma. Based on ultrastructural features, this tumor was an ectopic thyroid carcinoma.

Canine medullary carcinoma of the thyroid

An 8-year-old male Irish Terrior dog and a male St. Bernard dog each had a thyroid medullary carcinoma. The first dog was hypocalcemic before removal and with recurrence of the neoplasm. In both dogs the neoplasms were bilateral and microscopic metastases were seen only in the regional lymph nodes. Both neoplasms were characterized by a solid alveolar pattern separated by thin vascular stroma or a linear festoon-like arrangement with thick stroma. The neoplastic cells varied little and were polygonal or round with abundant pale eosinophilic and finely granular cytoplasm. There was little mitotic activity. Both carcinomas contained amyloid. Electron microscopically, the neoplastic cells had moderate nuclear pleomorphism, well developed Golgi complexes, and characteristic membrane-bound electron-dense secretory granules. In some sections, the secretory granule membranes were fused to the cytoplasmic membrane and the granules were in the extracellular space. In one carcinoma there were linear fibrillar structures with an average width of 7.8 nanometers similar to that of amyloid fibrils.

Spinal cord compression caused by a metastatic lesion from an aortic body tumour

An aortic body tumour in a 7-year-old wire-haired fox terrier with hind limb ataxia is described. A metastatic lesion in the dorsal arch of the eighth thoracic vertebra caused compression of the spinal cord. Radiographic techniques are discussed that enabled the position and extent of the primary tumour and its metastasis to be defined and allowed a provisional diagnosis of chemodectoma.

Mediastinal parathyroid adenocarcinoma in a dog

A tumor in the anterior mediastinum was found in an adult male German Shorthaired Pointer. The dog presented with hypercalcemia that varied with the removal and recurrence of the tumor. The neoplasm was characterized by an encapsulated multilobed grey-white soft mass with stroma, and the recurrent tumor infiltrated veins and the heart. The tumor consisted of groups of clear cells with well outlined cytoplasmic boundaries separated by thin vascular stroma. These cells had few organelles, scattered clumps of glycogen, clear cytosol and prominent infolding and interdigitating plasma membranes and desmosomes. The clinical, light and electron microscopic features were consistent with a functional neoplasm of parathyroid tissue origin.