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Myocardial Tumors Myocardial tumors refer to tumors that specifically affect the heart. These types of tumors are rare, and when they do occur, they tend to occur in older dogs. Benign tumors are masses of tissue that do not metastasize, whereas malignant tumors metastasize throughout the body. Shepherd dog. Tumors of the heart base arise either from aortic body or carotid body chemoreceptor organs and are collectively termed chemodectomas or heart-base tumors. Chemoreceptor organs are part of the parasympathetic nervous system and they are sensitive to changes in blood carbon dioxide concentrations, pH, and arterial oxygen tension. In the present case, left atrial wall and heart base were predominantly involved. Metastasis was not observed in the present case, similar to most other canine cases (6–8). The age of the dog presented in this case report was within the age-range of previously reported cases of cardiac fibrosarcoma in the dog (7 to 15 y) (6–8).
Abstract
- Mast cell tumors may occur as skin bumps or internal tumors. These masses may release histamine when disturbed, which can have a negative effect on your dog's body, including the heart. If your vet suspects a mast cell tumor, your dog may be treated first with diphenhydramine to minimize the histamine release.
- Mar 13, 2015 Heart base tumours in dogs are most commonly chemodectomas - a benign type of tumour arising from the aortic chemoreceptor cells.
An adult Labrador retriever dog was presented with respiratory signs and heart murmur. Echocardiography and thoracic radiographs revealed a heart base mass infiltrating the left atrial wall. Microscopically, neoplastic tissues consisted of spindle cells and abundant extracellular matrix. Based on histochemical stain and immunohistochemistry, a diagnosis of primary cardiac sarcoma was made.
Résumé
Tumeur cardiaque primaire à cellules fusiformes chez un chien. Un chien Labrador Retriever adulte a été présenté avec des signes respiratoires et un souffle cardiaque. L’échocardiographie et les radiographies thoraciques ont révélé une masse à la base du cœur infiltrant la paroi atriale gauche. Au microscope, les tissus néoplasiques se composaient de cellules fusiformes et d’une matrice extracellulaire abondante. En se fondant sur la coloration histochimique et l’immunohistochimie, un diagnostic de sarcome cardiaque primaire a été posé.
(Traduit par Isabelle Vallières)
An 11-year-old, neutered female, Labrador retriever dog was presented to the Cardiology Service at the North Carolina State University Veterinary Teaching Hospital (NCSU-VTH) for evaluation of loss of appetite, cough, and a newly diagnosed 3/6 heart murmur. For 1 mo prior to presentation, the dog exhibited a non-productive cough, panting, compulsive pacing, and whining. The cough occurred 2 to 3 times per day and was most frequently noted when the dog stood after sitting or lying down. No episodes of respiratory distress had been noted by the owner. A murmur was noted during physical examination by the primary veterinarian 1 wk prior to presentation, which resulted in referral to the NCSU-VTH.
Case description
On presentation, the dog had a heart rate of 150 beats/min, a regular rhythm with occasional premature beats, and a grade 3/6 left-apical systolic murmur. Lung sounds were increased in all fields and a cough could be elicited with tracheal palpation. Thoracic radiographs revealed mild left ventricular enlargement and focal elevation of the trachea proximal to the carina. This latter finding was suggestive of a heart base tumor, yet it could not be corroborated on the dorsoventral or left lateral view. The echocardiograph revealed a large, multilobular mass that filled approximately 80% of the left atrial lumen, which was moderately dilated. Disruption of left ventricular filling was evident on color Doppler by turbulent flow around the mass during diastole (Figure 1) and an elevation in the trans-mitral inflow velocity (1.6 m/s). Mild mitral insufficiency secondary to disruption of the mitral valve annulus was the cause of the systolic murmur. The moderate left atrial enlargement was suspected to be due to both obstruction to left ventricular inflow and mitral insufficiency. The electrocardiograph revealed sinus tachycardia with occasional supraventricular premature complexes. Due to the progression of cough and apparent discomfort (pacing, vocalization), the dog was euthanized 2 wk after presentation and a complete necropsy was done.
Echocardiograph of the heart mass in the dog. Transthoracic left apical view with color Doppler demonstrates the mass within the left atrium and turbulent flow within the left atrium during diastole.
The necropsy revealed a fairly demarcated, unencapsulated, multinodular, raised, spherical mass, 8 cm × 5 cm × 4 cm in size, at the heart base near the base of aorta. The mass markedly protruded towards and occupied approximately 80% of the left atrial lumen (Figure 2). The mass was firm and white and mottled with multifocal hemorrhagic foci on the cut surface. The left atrium and right and left ventricles were mildly dilated. The thickness of the right and left ventricular walls was grossly within normal limits. The valvular cusps were grossly unremarkable. The pericardium contained 30 to 50 mL of serosanguineous fluid. There was no gross evidence of metastasis to distant organs or regional lymph nodes. The lungs were mildly congested and edematous, which were microscopically supported by slightly increased foamy or hemosiderin-laden alveolar macrophages. Touch impression smears of the mass revealed a few clusters of a spindle cell population with round large nuclei with moderate amounts of cytoplasm.
Gross image of the heart mass in the dog. The left atrial wall has a demarcated, unencapsulated, multinodular, raised, spherical mass measuring 8 cm × 5 cm × 4 cm protruding towards and occupying approximately 80% of the left atrial lumen. The aorta is slightly compressed but has no evidence of tumor invasion on the intimal surface.
Histologically, the mass was an infiltrative, unencapsulated neoplasm composed of spindle cells arranged in sheets and interlacing short bundles that replaced and separated pre-existing myocardial fibers (Figure 3). Neoplastic cells had moderate amounts of eosinophilic cytoplasm with indistinct cell borders, oval to fusiform vesicular nuclei with finely stippled moderate chromatin, and 1 to 2 magenta nucleoli. Multifocally, neoplastic cells were embedded in moderate to large amounts of eosinophilic fibrillar extracellular matrix that was strongly stained by Masson’s trichrome as a blue color (Figure 4). Anisocytosis and anisokaryosis were moderate and mitotic figures were up to 5 per high power field. Throughout the mass, there were multifocal areas of extensive hemorrhage and necrosis. There was no histological evidence of metastasis within the other organs examined (lungs, tracheobronchial lymph nodes, gastrointestinal tract, liver, spleen, kidney, urinary bladder, brain, pituitary gland, thyroid glands, adrenal glands, and pancreas).
Photomicrograph of the heart mass in the dog. Histologically, the mass is infiltrative, the unencapsulated neoplasm replaces and separates pre-existing normal right arterial wall. The neoplasm is composed of spindle cells arranged in sheets and interlacing short bundles. Multifocally, neoplastic cells are embedded in moderate to large amount of eosinophilic fibrillar extracellular matrix. Hematoxylin and eosin stain. (Bar = 800 μm)
Dog, heart mass, photomicrograph, Masson’s trichrome stain. The extracellular matrix surrounding neoplastic cells is strongly stained blue, suggesting that it is collagenous. (Bar = 300 μm)
Microscopic appearance of the heart base mass in this dog was consistent with spindle cell sarcoma and further evaluation was performed for differential diagnosis. Ectopic thyroid carcinoma, myxosarcoma, osteosarcoma, chondrosarcoma, granular cell tumor, lymphoma, hemangiosarcoma, malignant mixed mesenchymoma, lymphangiosarcoma, and angiolipoma were ruled out based on the microscopic features of the neoplasm. In order to determine the lineage of the neoplastic spindle cells, serial sections of the tumor mass were subjected to immunohistochemistry (IHC). For IHC, the standard avidin-biotin peroxidase technique (Labeled Streptavidin-Biotin2 System-Horseradish Peroxidase, Dako, Carpinteria, California, USA) and commercially available antibodies were used to detect vimentin (monoclonal antibody, clone V9, Dako), cytokeratin (monoclonal antibody, clone AE1/AE3, Dako), smooth muscle actin (SMA) (monoclonal antibody, clone 1A4, BioGenex, Fremont, California, USA), desmin (monoclonal antibody, clone 33, BioGenex), chromogranin-A (polyclonal antibody, Dako), and S-100 (polyclonal antibody, Dako).
More than 80% of neoplastic cells showed strong cytoplasmic immunoreactivity for vimentin, but were negative for cytokeratin, smooth muscle actin (SMA), desmin, and chromogranin-A. Immunohistochemistry for S-100 was inconclusive due to non-specific background staining. Positive staining for vimentin indicated that the neoplastic spindle cells were of mesenchymal origin. Rhabdomyosarcoma and leiomyosarcoma were ruled out due to absence of typical morphological features and negative IHC results for desmin and SMA, respectively. Sarcomatous subtype of mesothelioma is expected to have dual positive for cytokeratin and vimentin, but the tissue was positive for vimentin only. The histologic features and negative IHC result for chromogranin-A were not consistent with chemodectoma (). Malignant peripheral nerve sheath tumor and neurofibroma were considered to be less likely given the lack of characteristic histological features and an inconclusive result with S-100 antibody. The origin of the neoplastic spindle cells in this case was determined as mesenchymal by strong positive staining for vimentin, and more specifically as fibroblastic in nature based on the extracellular collagenous matrix highlighted by Masson’s trichrome. The gross, microscopic, histochemical, and immunohistochemical findings led to the final diagnosis of this neoplasm as cardiac fibrosarcoma.
Cardiac tumors occur as primary and as metastatic lesions. In humans, the frequency of metastatic lesions has been estimated to be 20 to 40 times that of primary cardiac tumors, which have a reported incidence between 0.0017% and 0.19% (). Primary malignancies of the heart and greater vessels are rare in both humans and domestic animals (,). In humans the most common primary cardiac tumor is myxoma (). In dogs, hemangiosarcoma accounts for nearly 70% of primary cardiac tumors, followed by aortic body tumor (chemodectoma) (). Other primary cardiac tumors including fibrosarcoma, rhabdomyosarcoma, chondrosarcoma, osteosarcoma, myxoma, granular cell tumor, malignant mixed mesenchymal tumor, lymphangiosarcoma, angiolipoma, fibroma, neurofibroma, and mesothelioma are extremely rare in dogs (). Because there is no specific marker for fibroblastic lineage, IHC is rarely useful in making a diagnosis of fibrosarcoma in humans or animals. Diagnosis of fibrosarcoma in this case was made by exclusion of other spindle cell tumors, with support of histochemical staining (). In veterinary medicine, primary cardiac fibrosarcoma has been reported in multiple species including dogs (,–8). In dogs, approximately 1% of all primary heart tumors are cardiac fibrosarcoma (). Primary cardiac fibrosarcoma in dogs has been reported to involve the right ventricular free wall, endocardium of the right atrium, interatrial septum, and interventricular septum (–8). Pulmonary metastasis was reported in 1 of these cases (). In the present case, left atrial wall and heart base were predominantly involved. Metastasis was not observed in the present case, similar to most other canine cases (–8). The age of the dog presented in this case report was within the age-range of previously reported cases of cardiac fibrosarcoma in the dog (7 to 15 y) (–8).
The clinical diagnosis and therapy of these tumors is difficult, as symptoms are often non-specific and evident only in advanced stages of the disease. Due to improvements in diagnostic imaging and surgical techniques, the probability of early diagnosis and successful resection has increased, yet the prognosis remains generally poor (–8). The prognosis of cardiac tumors depends on the structural and functional changes associated with their size and location (,9). Unfortunately, the neoplasm in this dog protruded into left atrium that receives oxygenated blood from the lungs and might affect left ventricular filling and subsequent cardiac output. The intermittent cough was likely due to compression of the left mainstem bronchus resulting from left atrial dilation.
This case report presents a detailed description of a primary cardiac spindle cell sarcoma in an elderly dog presenting with respiratory signs. It serves to broaden the diagnostic spectrum of cardiac and respiratory diseases in dogs.
Acknowledgments
We thank Sandra Horton and the histology staff of Histology Core Laboratory, North Carolina State University, for their technical support. CVJ
Footnotes
Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (gro.vmca-amvc@nothguorbh) for additional copies or permission to use this material elsewhere.
References
What is a chemodectoma?
Dmg Heart Base Tumor Dog Food
A chemodectoma is a type of tumor made up of chemoreceptor cells. Chemoreceptorcells detect chemical changes (such as oxygen content and pH levels) in the body and respond by regulating chemical or physical processes. A chemodectoma involves abnormal growth of these chemoreceptor cells in an uncontrolled way that causes the formation of a tumor.
The most common regions these tumors are seen are along one of the carotid arteries and the aorta. Two carotid arteries sit within your pet’s neck; one on each side of the trachea. The aorta is the large blood vessel that leaves the heart to deliver oxygenated blood to the body. These tumors are rare and may be found when your pet has a wellness examination or if your pet is exhibiting signs associated with these tumors.
What causes this type of tumor?
The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary.
In the case of chemodectomas, short-nosed breeds (brachycephalic breeds), are more predisposed to these types of tumors (e.g., Boston Terriers and English Bulldogs). Because these breeds have chronic low oxygen levels due to the structure of their face, jaw, and airway, it is thought that the chemoreceptors are overworked, and tumor development occurs. German Shepherds and Boxer Dogs, as well as male dogs tend to be more predisposed to aortic body tumors.
Dmg Heart Base Tumor Dogs
What are the signs of chemodectomas?
Clinical signs of chemodectomas depend on the location of the tumor. The most common clinical signs associated with aortic tumors (located on the aortic artery) and the resulting pericardial effusion (fluid within the sac around the heart) include weakness/wobbliness, lethargy, collapse, exercise intolerance, increased respiratory rate and effort, cough, vomiting, and sudden death.
The most common signs associated with a carotid artery tumor (located in the neck) are swelling in the neck region, regurgitation, lethargy, difficulty breathing, weakness, and collapse.
How is this cancer diagnosed?
Your veterinarian may notice changes in your pet during a wellness examination such as increased breathing rate and effort, and swelling in the neck region. Your veterinarian may recommend radiographs (X-rays) or ultrasound of the chest, which may show evidence of a tumor in front of or around the heart, or fluid within the sac around the heart (called pericardial effusion). More commonly though, ultrasound or a CT scan of the chest and neck will show evidence of tumors.
'Your veterinarian may notice changes in your pet during a wellness examination such as increased breathing rate and effort, and swelling in the neck region.'
Once a diagnosis of a mass on the carotid artery or aorta is made, your veterinarian may discuss performing an ultrasound-guided fine needle aspiration. Other techniques involving specialized equipment to obtain samples of carotid tumors and may be discussed. These techniques use an ultrasound probe to guide a small needle into the tumor to retrieve cells. The cells are placed on a microscope slide which is examined by a veterinary pathologist.
If the mass is close to the heart, these diagnostic techniques have significant risk of complications including bleeding. Because of these risks, once a mass has been diagnosed, surgical removal of the tumor may be recommended. Samples of the tumor will be examined under the microscope by a pathologist who will confirm the tumor type.
How does this tumor typically progress?
Carotid and aortic body tumors are commonly locally aggressive. This means that they penetrate the local tissues directly surrounding the area where they form. However, there are rare cases of metastasis (spread) to other organs including the lungs, lymph nodes, and bone.
What are the treatments for this type of tumor?
The most commonly pursued treatment is surgical removal of the tumor, regardless of location.
Your veterinarian may discuss with you the options for a pericardectomy. This involves removing the tumor as well as a part of sac that surrounds the heart (the pericardium). Pets that have a pericardectomy have improved recovery and live significantly longer.