Canine Cancer Thyroid Gland Neoplasia

Canine Cancer Thyroid Gland Neoplasia

Cancer in dogs Thymus Gland Neoplasia

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Description

All tumors found in dogs range from 1.2 % to 3.8 % thyroid gland neoplasia. According to their follicular origin, they can be categorized as papillary, follicular, compact, or anaplastic. Dogs are most typically found with follicular and compact subtypes.

Boxer, Golden Retriever, and Beagle breeds are particularly prone. Older dogs are more likely to develop thyroid gland tumors. But no gender preference has been noted thus far. The thyroid gland's lobes also suffer significant damage. On a very infrequent basis, lesions in the tongue, ventral neck, cranial mediastinum, and heart base might result from ectopic thyroid tissue (abnormal migration of thyroid tissue during embryonic development). In around 80% of instances, thyroid gland cancers eventually spread, making them very aggressive.

The metastatic sites may include the lungs as well as local lymph nodes such the retropharyngeal lymph node, which is located behind the top part of the throat in front of the atlas, the cervical lymph node, and the mandibular lymph node, which is located close to the jaw. However, only at the time of the initial presentation are metastases reported in about 35 to 40% of instances.

Causes

The cause of thyroid gland neoplasia, like most malignancies, is unknown. The range of the median survival period for non-resectable cancers treated with radiation therapy is 8 to 22 months.

Symptoms

The tumor manifests itself in dogs as a palpable ventral cervical lump. Coughing, fast breathing, dyspnea, trouble swallowing, dysphonia, and facial edema are some of the less frequent clinical symptoms (build up of fluid in the tissues of the face). Compression of the cervical artery can occasionally cause acute bleeding. Other clinical signs of hyperthyroidism in dogs may include wasting muscles, polyuria, polydipsia, and polyphagia (excessive hunger, thirst, and urination) (a wasted muscle is one which becomes thinner).

Diagnosis

Thorough physical examination, complete blood count, chemical panel, urinanalysis, three-view thoracic radiography, cytologic or histologic assessment of the local lymph nodes, and cervical ultrasonography are some of the usual diagnostic procedures used to find thyroid carcinoma. These techniques assist in determining the stage of the disease.

Cervical ultrasonography is helpful in determining the thyroid mass's origin, vascularity, and aggressiveness. Additionally, because of the high vascular density of malignant tumors and hemodilution (an increase in blood fluid volume), aspiration techniques designed to lessen hemodilution are used, and a differential diagnosis of endocrine tumors is made based on an examination of the feather edge. In addition, procedures for large core needle biopsy are at danger due to the increased vascular density.

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The cytologic or histological evaluation method for thyroid masses is not infallible since it is unable to identify the tumor's primary site in more than half of the afflicted instances.

Typically, metastatic illness is checked for in the retropharyngeal and cranial lymph nodes.

Treatment

The course of treatment is determined by the size of the tumor, the degree of infiltration, the presence or absence of metastases, and the presence or absence of symptoms of thyrotoxicosis (condition in which the thyroid gland produces excessive hormone). Only non-metastatic tumors can be treated with a thyroidectomy, which involves surgically removing the entire thyroid gland. Surgery is avoided if it is discovered that the disease also affects nearby structures such as the vasculature (the arrangement or distribution of blood vessels), recurrent laryngeal nerves, parathyroid glands (small endocrine glands in the neck that produce parathyroid hormone), and occasionally the larynx and trachea.

It becomes exceedingly challenging to surgically remove the lesion if the condition worsens to a life-threatening level without harming the laryngeal nerves, which could cause laryngeal paralysis, aspiration pneumonia (which arises when foreign objects enter the bronchial tree), and finally death. Acute hemorrhage can occasionally result from coagulopathy (a malfunction in the body's system for clotting blood), vascularity of the tumor, infiltration into the surrounding blood arteries, and other factors.

External beam radiation therapy can be used to treat thyroid cancers that cannot be surgically removed. Hypofractionated radiation therapy, however, might offer momentary relief for canines who have large metastases. With variable degrees of success, the use of chemotherapy in the treatment of bilateral, metastatic cancers has been examined. Dogs who are more likely to acquire metastatic disease are treated with systemic chemotherapy or final chemotherapy.

Prognosis

The degree of infiltration has a significant impact on the prognosis. Three years has been shown to be the median lifespan of dogs who underwent thyroidectomy. However, if the tumor is more aggressive, the survival rate drops to 6–12 months. However, some factors, such as thyroid stimulating hormone (TSH), thyroid radiation, and a lack of thyroid hormone replacement, have been suggested to contribute to the growth of thyroid gland cancers. A median survival time of 1-3 years was observed in dogs who underwent incomplete thyroidectomy followed by radiation therapy. Radiation treatment extended the overall life duration of dogs with substantial metastases to 22 months. A partial remission was observed in 30–50% of the dogs who received doxorubicin or cisplastin treatment.

By PetsCareTip.Com