Thyroid Cancer

[Dr.Sudan]

There are four main types of thyroid cancer (in order of frequency):

1. Papillary
2. Follicular
3. Medullary
4. Anaplastic

Follicular thyroid carcinoma (FTC) is a well-differentiated tumour. In fact, FTC resembles the normal microscopic pattern of the thyroid. FTC originates in follicular cells and is the second most common cancer of the thyroid after papillary carcinoma. The most common presentation of thyroid cancer is an asymptomatic thyroid mass, or a nodule, that can be felt in the neck.

The staging of well-differentiated thyroid cancers is related to age for the first and second stages but not related for the third and fourth stages.

Younger than 45 years:

Stage I: Any T, any N, M0 (Cancer is in the thyroid only).
Stage II: Any T, any N, M1 (Cancer has spread to distant organs).

Older than 45 years:

Stage I: T1, N0, M0 (Cancer is in the thyroid only and may be found in one or both lobes).
Stage II: T2, N0, M0 and T3, N0, M0 (Cancer is in the thyroid only and is larger than 1.5 cm).
Stage III: T4, N0, M0 and any T, N1, M0 (Cancer has spread outside the thyroid but not outside of the neck).
Stage IV: Any T, any N, M1 (Cancer has spread to other parts of the body).

Surgery is the definitive management of thyroid cancer. Various types of operations may be performed:

Lobectomy with isthmectomy
This is the minimal operation for a potentially malignant thyroid nodule. Patients less than 40 years who have FTC nodules less than 1 cm, well defined, minimally invasive, and isolated may be treated with hemithyroidectomy and isthmectomy.

Subtotal thyroidectomy (small part of contralateral lobe retained)
If feasible, subtotal thyroidectomy is preferable since it carries a lower incidence of complications (for example, hypoparathyroidism, superior and/or recurrent laryngeal nerve injury).

Total thyroidectomy (removal of all thyroid tissue preserving the contralateral parathyroid glands)
Approximately 10% of patients who have had total thyroidectomy demonstrate cancer in the contralateral lobe. Total thyroidectomy should be performed in patients who are more than 40 years with FTC and in any patient with bilateral disease. Total thyroidectomy is recommended for any patient with a thyroid nodule and a history of irradiation. Some studies show lower recurrence rates and increased survival rates in patients who have undergone total thyroidectomy. This surgical procedure also facilitates earlier detection and treatment of recurrent or metastatic carcinoma.

Patients receive radioiodine four to six weeks after thyroidectomy to detect and destroy any metastases and any residual tissue in the thyroid.

Following thyroidectomy, patients will need to take thyroid replacement therapy.

External beam radiation is used in the management of FTC if the cancer cannot be resected, or if there is extension into adjacent structures. Radiotherapy may also be administered postoperatively to reduce the risk of local-regional recurrence. It may also be used palliatively to treat pain from bone metastases.

Chemotherapy with cisplatin or doxorubicin has limited efficacy. It may be employed when other treatment modalities have failed