Thyroid cancer - The Good, the Bad and the Ugly

Dr (Major) Anil Ayekpam *

The thyroid is an Endocrine organ present in the front of the neck. It is a butterfly shaped organ with two lobes connected by an Isthmus. The thyroid produces the thyroid hormone, which is needed for metabolism. Another cell in the thyroid called the 'C cells produces the hormone calcitonin, which is needed for maintaining the levels of calcium in the body.

Cancer of the thyroid is the 9th commonest malignancy worldwide and is increasingly detected over the past few decades. The increased incidence is mainly due to incidental detection due to increased use of Ultrasound and CT Scan Neck for various diagnostic purposes. The thyroid cancer can be of 4 types -Papillary, Follicular, Medullary and Anaplastic types.

Papillary and Follicular are called well Differentiated Thyroid Cancers (DTCs) because they maintain some characteristics of the normal thyroid follicular cells and constitutes about 90% of all thyroid cancers. The Medullary type arises from the 'C' cells of thyroid and comprises between 5-10% while the anaplastic cancers are rare and constitute around 1 -2% of all thyroid cancers.

Thyroid Cancer usually present as a mass in the front of the neck, mass may deviate to the right or the left side of the neck depending on the location on either the right or left lobe. Sometimes a swelling on the side of the neck may represent a metastatic lymph node, more common in the papillary type.

The Follicular type usually presents as a mass in the neck and is less prone to spread to neck nodes and may present as a swelling in the scalp or elsewhere, when it is metastatic. The Anaplastic variety may arise from a long standing benign thyroid goitre or as a rapidly enlarging mass in the front of the neck.

Thyroid Cancers are usually diagnosed when a mass in the neck is being investigated. Clinical examination by a doctor, an Ultrasound of the neck and the FNAC of the swelling is usually sufficient for a diagnosis of thyroid cancer. Primary treatment usually consists of removing a lobe of the thyroid (Hemithyroidectomy) or the whole thyroid (Total Thyroidectomy) and removal of the neck nodes if enlarged.

In the case of DTCs surgery is usually followed by treatment with Radioactive Iodine (RAI) Therapy according to the risk of spread and further Iodine Imaging. RAI uses a radioactive substance tagged to Iodine, which emits Gamma rays to kill cancerous cells spread outside of the thyroid bed or left on the thyroid bed after surgery.

RAI therapy is done by trained Nuclear Medicine Physician under well design environment to reduce radiation hazards. It is given orally as a liquid.

THE GOOD THYROID CANCER

The well differentiated thyroid cancers (pallillary and follicular types) are usually diagnosed when localized in the neck. Since they maintain some characteristics of the normal thyroid follicular cells, they take up Iodine.

It is this property of DTCs where Radioactive Iodine Therapy can be used to treat these thyroid cancers. The prognosis is usually very good and cure rates are >95%. Only a very small portion of these cancers can transform into other cell types -a condition known as TENIS Syndrome (Thyroglobulin Elevated Negative Iodine Scintigraphy) where Radioactive Iodine Therapy fails having grave prognosis.

THE BAD THYROID CANCER

Medullary Thyroid Cancers are derived from 'C cells and are caused by mutation in the RET gene, may occurs sporadically or associated with syndromes such as Multiple Endocrine Neoplasia. They may behave like neuroendocrine tumours.

These tumours do not concentrate Iodine, therefore Radioactive Iodine Treatment are not effective. These patients usually have a 80-90% 5 years survival rate and can be considered the Bad Thyroid Cancer.

THE UGLY THYROID CANCER

Fortunately, the Anaplastic varieties of thyroid cancers are the rarest. They are very aggressive and have a very poor prognosis with a median overall survival of less than 6 months. All Anaplastic cancers are considered to be Stage IV in the prognosis classification.

Treatment involves a multi-disciplinary approach involving Endocrinologist, Surgical Oncologist, Medical Oncologist, Radiation Oncologist and Palliative Care.

The presentation of the thyroid cancers is one of the most diverse of all cancers. Some of them will never require treatment during an individual's lifetime and some in spite of all the medical advances, continues to have a very grave prognosis. The risk of a person developing any type of cancer in his or her lifetime is estimated to be 1 in 3.

To sum up all, if I had the liberty to choose for myself, I will choose the good thyroid cancer first and the Anaplastic thyroid cancer the last.