Cancer: Thyroid

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Overview - Thyroid Cancer in Dog

There are several different types of thyroid cancers including adenomas, carcinomas and tumors generated by c-cells.

C-cells are not cancerous cells, (called medullar thyroid cells or parafollicular cells) but they cause or trigger a form of carcinoma in the thyroid gland. In effect they are stem cells for the thyroid gland.

Adenomas are nodular (masses), that have a gray to tan appearance. These tumors are benign (slow growth), however they impact the production of thyroid hormone. Benign tumors such as Adenomas are easy to treat by lobectomy (surgery to remove all or part of the thyroid) and radiation therapy.

Carcinomas on other hand involve metastases; meaning it can spread to other parts of body via blood circulation. Carcinomas can produce a large number of nodules at the thyroid gland. As a carcinoma nodule diffuses or spreads through the thyroid it causes the thyroid itself to degrade, resulting in severe thyroid disease.

Thyroid cancer is characterized by symptoms that are not specific to the disease. It may mimic the symptoms of other canine thyroid diseases. Because of this testing is required for a definitive diagnosis.

Treatment via surgery to remove the diseased lobe or part of the thyroid (lobectomy) is effective along with chemotherapy and radiation therapy. The prognosis or outcome for dogs depends upon the type and severity of the cancerous cell growth and if the disease returns after treatment.


Dogs may exhibit signs of various thyroid diseases associated with abnormal functioning of the thyroid gland. Cancerous cells may affect the functioning of the thyroid gland in many ways.

Some of the signs are weight loss, loss of appetite, hyper salivation, and mild fever. Dogs may have a lump in the skin and hard nodules that can be felt at apex of the neck. Difficulty in respiration (breathing) and swallowing may be due to nodular pressure at the trachea and esophagus respectively.

Dogs may also show signs of either hyperthyroidism or hypothyroidism.


As mentioned, the key to diagnosis is to determine if symptoms are due to canine thyroid cancers vs other thyroid in dog conditions.

For example, a lump at apex of neck may either be due to thyroid cancer or it may be a due to a non neoplastic (not cancerous) inflammatory growth or a goiter.

Similarly, irregular hormonal release that of T3, T4 & thyroid stimulating hormone (TSH) may often be confused with hyperthyroidism or hypothyroidism. So in this regard, common tests and procedures may never be helpful in diagnosing a canine thyroid cancer. A specific and descriptive biopsy (tissue sample) is usually required to confirm that there is a cancerous development in the thyroid. Secondary lymphoid sarcomas (cancer cells in the lymph glands) may help in predicting a primary canine thyroid cancer (cancer that starts in the thyroid vs a secondary which means that the cancer spread to the thyroid from elsewhere in the body).


Surgical resection is only effective if the degree of canine thyroid cancer is low. If cancerous cells exist deep in the thyroid and if the cells are scattered, it decreases the effectiveness of surgery as an option.

In most of cases, the return of the cancer is common due to the difficulty of getting access to deeper tissues while operating.

Along with surgery, a combination of radiotherapy and chemotherapy has proven to be most effective in metastasis (cancers). Radiotherapy is considered very effective, but there are some concerns about its application. In many cases the waves are mostly too harmful for the cells which balance the secretion of hormones in the thyroid gland. If this is the case, dogs may exhibit irreversible thyroid problems.

If there is concern that radiation therapy may be harmful, then milder radiation is used in addition to surgery and chemotherapy.

Given the seriousness of this disease, and while it is not a cure for cancer, it may be worth supplementing your dog's diet with a homeopathic remedy. Two products to consider and research are C-Caps Formula , which supports the immune system, and Thyroid Soothe , which is manufactured to support the thyroid gland itself.


The prognosis for cancer dog thyroid depends upon the type, location how far the cancerous tumor has spread. Usually in nodular forms the prognosis is very good, while cancers that spread or diffused have a weaker prognosis.

The recovery time whether or not it has returned after treatment goes into determining if the canine thyroid cancer is fatal or not. In most cases, dogs that have recovered from any form of thyroid cancer develop secondary problems of thyroid gland and lymphatic suppression. Lymphatic suppression refers to reduced activity and performance of lymphatic tissues. The lymph system of the body when working correctly, removes bacteria and certain proteins from the tissues, transport fat from the small intestine, and supplies mature lymphocytes to the blood. Problems with the thyroid and lymphatic tissues reduce the chances of recovery.