Diseases related to thyroid are common worldwide. Most of these diseases are benign and not dangerous. About 5 percent of thyroid disorders can be malignant. These generally present in the form of thyroid enlargement. Thyroid cancers can be of various types. Commonest amongst all is Papillary carcinoma of thyroid. Other cancers can be Follicular carcinoma, Medullary carcinoma, Anaplastic carcinoma, Lymphoma etc.
The cause varies according to the type of cancer. Papillary carcinoma is associated with childhood exposure to radiation, family history of thyroid cancer and certain genetic mutations. Medullary carcinoma in 25 percent of cases may be familial; in such cases it is associated with syndromes like MEN IIa and MEN IIb. These cases have specific genetic mutations present which are passed on in the family. Follicular cancer and lymphoma are seen in iodine-deficient areas. Anaplastic cancer occurs in long standing thyroid swellings. Thyroid cancers are common in females and are seen more often in the age group of 40-50 years.
Thyroid cancers present commonly as neck swelling. It may generally be a single swelling or multiple. It may be associated with neck node enlargement. Patients may have associated symptoms of hypothyroidism such as – weight gain, decreased appetite, decreased sweating, intolerance to cold etc. Family history of thyroid cancer or swelling may be present. There may be a history of exposure to radiation or radiotherapy in childhood. Sometimes a long standing thyroid swelling may start increasing in size rapidly. In case of very large swellings or advanced cancer windpipe or food pipe may be compressed leading to difficulty in breathing or swallowing. Many times hoarseness of voice may also be present. If the thyroid cancer has spread to distant sites such as bone then the patient may present with bone pain or a fracture of bone following a trivial trauma or insult.
A patient of thyroid cancer requires a thorough clinical examination. Size and extent of swelling is noted. Using an endoscope status of the vocal cords is also noted, as they may be affected because of disease involving the nerve supplying them. Thyroid function tests are done. These include T3, T4 and TSH. Ultrasonography examination of the neck is a must. With its help, the extent and nature of the swelling is noted. It also helps in identifying the presence of lymph node enlargement or multiple small nodules in the thyroid itself. Fine needle aspiration cytology (FNAC) from the thyroid swelling is done. The slides prepared through this procedure are seen under a microscope to assess what types of cancer cells are present. Many times, direct FNAC may not give a proper result. In such cases, ultrasonography guided FNAC is done. If the thyroid swelling is big and is extending to the chest or compressing the food and wind pipe then a CT scan of neck and chest may also be asked for. If it is felt that the cancer has spread to distant sites then a bone scan or PET scan may also be done.
Treatment of thyroid cancer depends on various factors. These include age, sex, size of the lesion, and presence of lymph node metastasis or distant metastasis. Surgery is the treatment of choice in most of the cases. Treatment is tailored to suit individual patients. Surgical excision of thyroid gland may entail a hemi-thyroidectomy or a total thyroidectomy. In hemi-thyroidectomy only half of the gland on the affected side is removed. In total thyroidectomy, the entire thyroid gland is removed. Besides removal of thyroid gland, lymph nodes present in the neck may also require to be removed. If lymph nodes in the chest are also involved then they are removed too.
Common complications associated with thyroid surgery include vocal cord palsy and/or hypocalcemia. If the nerve supplying the vocal cord is injured during surgery or requires to excised due to involvement of the disease then the patient may develop hoarseness of voice. It may be temporary or permanent. Permanent cord palsy may occur in less than 5% of cases. During thyroid surgery if the blood supply to parathyroid glands (related to calcium balance) is affected then the patient may develop hypocalcemia where the blood level of calcium decreases. This may also be temporary or permanent and may require supplementation of calcium. If complete thyroidectomy has been done then the patient may require life-long supplementation of thyroid hormone.
Many times, patients require post-surgery radio-iodine scan and therapy. Before doing the scan the patient is kept on an iodine-free diet. If the radio-iodine scan shows presence of distant spread or residual disease then further ablation with radio-iodine may be required. After radio-iodine therapy, certain precautions need to be taken to prevent exposure of adjoining people to radiation. If during surgery complete excision of the lesion is not possible then post-operative radio-therapy may be required. If there is spread of disease to distant bony sites then radio-therapy may be given to those sites too.
Generally thyroid cancers have a very good prognosis and survival. Anaplastic thyroid cancer has a poor prognosis. Chemotherapy is used to treat these cancers. Thyroid cancer patients are generally reviewed 6 monthly to annually to look for presence of any residual disease or recurrence. Periodic clinical examination, ultrasonography, thyroglobulin are used to monitor the disease status.