Chemodectomas are mostly benign tumors that originate from chemoreceptor tissues of the body. Chemoreceptor tissues are those tissues which are very sensitive and responsive to chemical stimuli. These tissues are most sensitive to chemical changes in the body, such as oxygen content and pH levels in the blood.
Although chemoreceptor tissues can be located througout the body, chemodectomas most commonly affect chemoreceptor organs, i-e, aortic body (one of several small clusters of chemoreceptors in the heart) and carotid body (a small mass of chemoreceptors in the carotid artery). Therefore, the two most common types of chemodectoma are aortic body tumor in the heart-base region and carotid body tumor in the neck.
Aortic artery near the base of the heart is the most common place for aortic body tumors. Although the tumors are rarely malignant and do not spread to other parts of the body, they become problamatic when they displace trachea due to growth, grow into the adjacent vessels or when their growth puts pressure on the atria or vena cava, impairing their functionality.
Carotid tumors, on the other hand, occur on common carotid artery near the point where the artery divides into internal and external carotid arteries. As these arteries carry oxygenated blood to the head and neck, and are located in the neck, the removal of carotid body tumors is near impossible. These tumors remain benign but become health concern when they invade the spaces of the adjacent blood vessels and lymphatic vessels. Metastasis does occur in about 30% of carotid body tumors into surrounding organs, such as the lungs, bronchia or lymph nodes, or further into the liver or pancreas.
Chemodectomas are uncommon in dogs and although they are mostly benign tumors, they can behave like a malignant tumor. It is estimated that about 80% to 90% of chemodectomas are aortic body tumors. There is a breed, age and sex predilection with boston terriers and boxer, over 10 years of age, are the most commonly affected breeds. Male dogs are predisposed to aortic body tumor while there is no sex predilection for carotid body tumor.
Common signs associated with these two types of tumors include
Aortic body tumor
Signs of congestive heart failure
Carotid body tumor
Other signs (in either form)
Severe hemorrhaging due to tumors in the blood vessels (can lead to sudden death)
Metastasis to local blood vessels (up to 50 percent of cases )
Organ failure due to cancerous growths (up to 20 percent of cases)