Thyroid & Parathyroid Problems
Lumps and nodules in the thyroid gland are extremely common. Most of these nodules are benign. Occasionally a nodule turns out to be a thyroid cancer. Thyroid cancer is more common in women and may affect all age groups even children. Differentiated thyroid cancer is more common in areas of iodine deficiency and in people previously exposed to radiation.
Most patients with thyroid cancer have an enlarging lump in the thyroid gland that they can see or feel. This may have the worrying features of a hard texture or rapid growth or it may be asymptomatic. The lump can rarely press on the windpipe or oesophagus and cause difficulty with swallowing or breathing. Rarely thyroid cancers can damage the nerves that move the voice-box (recurrent laryngeal nerves) leading to a hoarse voice. Thyroid cancers may spread to the lymph glands of the neck and cause swollen lymph nodes. Sometimes this can be the first sign of a thyroid cancer. In medullary thyroid carcinoma there may be a family history of thyroid or other endocrine tumours.
How is thyroid cancer diagnosed?
The diagnostic tests used to confirm a thyroid cancer are the same as those used for thyroid nodules. Cancer may present as a solitary nodule, a dominant nodule in a multi-nodular goitre, rarely in the wall of a thyroid cyst or as swollen lymph glands (papillary cancer). The steps in the diagnosis however remain largely the same. They are:
What are the different types of thyroid cancer?
Cancers in the thyroid gland are grouped together based on the appearance of the cells under the microscope and on their behaviour (aggressiveness). Some of the more common types of cancer include:
Well differentiated thyroid cancers
Papillary thyroid cancer
Papillary thyroid cancers are the most common types of thyroid cancers represent 80% of all thyroid cancer. Women are more commonly affected than men. All age groups are affected including children. Predisposing factors include iodine deficiency and exposure to radiation. The disease at presentation is commonly multi-centric and has often spread to the cervical lymph nodes. Treatment is with surgery (usually total thyroidectomy and neck dissection if involved lymph nodes present) followed in most cases by a course of radio-active iodine and lifelong suppression of thyroid function with thyroxine. Surveillance may be carried out by repeat measurement of serum thyroglobulin. It has the most favourable prognosis of all thyroid cancers with more than 90% of patients alive after 5 years.
Follicular neoplasms are of two types; the benign, encapsulated follicular adenoma and invasive follicular carcinoma. Unfortunately they can only be differentiated on histology following excision and not by pre-operative FNAC. Follicular cancer spreads haematogenously to distant sites in around 30% of patients. Treatment is the same as papillary thyroid cancer. Survival however is worse for follicular cancers.
Medullary thyroid cancer (MTC)
This tumour arises from the para-follicular or C cells which secrete calcitonin. It is seen more commonly as a sporadic form but it may be familial. Many familial cases are in combination with other endocrine neoplasms as part of the Multiple Endocrine Neoplasia 1 or 2 syndromes. Most affected family members carry the RET proto-oncogene mutation and this is increasingly used for screening asymptomatic family members (often children). MTCs secrete calcitonin and this is a useful tumour marker especially for disease recurrence following treatment. Treatment is with total thyroidectomy and meticulous neck dissection.
Anaplastic thyroid cancer
This is an aggressive and invariably fatal neoplasm. It is seen in elderly patients who often present with a rapidly enlarging thyroid mass which may invade local structures causing dyspnoea, hoarseness and dysphagia. It is often difficult to diagnose as the clinical and FNAC appearances may be very similar to lymphoma. Occasional core or open biopsy is necessary to secure the diagnosis. Treatment is palliative and most patients die from their disease within months of diagnosis.