Chemodectoma in Dogs
Chemodectoma in canines is primarily benign tumors that originate from chemoreceptor tissue within the body. These tissues are highly sensitive to chemical variations such as oxygen levels and pH in the blood. Although chemoreceptor tissues are distributed throughout the body, chemodectomas predominantly affect the chemoreceptor organs, namely the heart and carotid artery.
While relatively uncommon in dogs, there are specific breeds and age groups that seem more susceptible. Boxers and Boston Terriers, particularly those older than ten years, are frequently affected. Moreover, there’s a tendency for males to be more predisposed to aortic body tumors, whereas carotid body tumors do not show any gender preference.
Symptoms and Types
Tumors found on the aortic artery, near the heart’s base, are termed aortic body tumors. Typically benign, these tumors grow locally without spreading to nearby organs. They pose health risks when they displace the trachea, extend into adjacent vessels, or exert pressure on the atria or vena cava, hindering blood flow. Indications of aortic body tumors include:
- Coughing
- Difficulty breathing
- Signs of right-sided congestive heart failure (CHF)
- Weakness, lethargy
Carotid body tumors, on the other hand, develop along the common carotid artery, close to its division point into internal and external branches. These arteries supply oxygenated blood to the head and neck. Given their proximity to major arterial pathways, removal of carotid body tumors is often challenging. Usually slow-growing and benign, these tumors become problematic when they invade adjacent blood and lymphatic vessels. In about 30 percent of cases, they may metastasize to nearby organs such as the lungs, bronchia, lymph nodes, liver, or pancreas. Symptoms associated with carotid body tumors encompass:
- Regurgitation
- Vomiting
- Difficulty eating (anorexia)
- Neck lump
Additional symptoms in dogs affected by either tumor type may include:
- Severe hemorrhaging from blood vessel tumors (potentially leading to sudden death)
- Metastasis to local blood vessels (in up to 50 percent of cases)
- Organ failure due to malignant growths (in up to 20 percent of cases)
Causes
There’s a suspicion that a chronic oxygen deficiency may contribute to the development of chemodectomas. This hypothesis could explain why flat-faced (brachycephalic) breeds are more prone to developing these tumors. Additionally, it’s believed that environmental factors may also play a role in tumor growth, with high altitudes potentially exacerbating oxygen deficiency (hypoxemia) in predisposed breeds.
Diagnosis
Upon conducting a comprehensive physical examination of your dog and gathering a detailed medical history, your veterinarian will proceed to order a chemical blood profile, complete blood count, urinalysis, and electrolyte panel. These tests’ results will offer insights into whether the cancer has spread within the body. If there’s hemorrhaging, anemia may be detected, and in cases of metastasis, elevated liver enzymes may be observed in the bloodstream.
Chest X-rays will be employed to pinpoint the mass’s location and to assess whether cancer has spread to the lungs or spine. Additionally, a cardiac ultrasound will be conducted, and if there are suspicions of heart impairment, an electrocardiogram (EKG) might be administered to evaluate the heart’s electrical signal conduction. If feasible, a tissue sample will be obtained from the mass for biopsy, providing a definitive diagnosis.
Treatment
Regrettably, the prognosis for dogs afflicted with either of these tumor types is typically bleak. Removing these tumors is often challenging, and they tend to persistently grow until they impede the functionality of surrounding vessels or organs, potentially leading to cardiac arrest or organ failure. Cancer treatment modalities such as radiotherapy may occasionally be employed in conjunction with surgery to retard the spread of these cancers.
Living and Management
It’s essential for your dog to undergo regular re-evaluation by your veterinarian, with chest X-rays and physical examinations scheduled at least every three months. These assessments are crucial for monitoring potential recurrence or spread of the cancer.
