Diagnosis of Thyroid Cancer

Author : Bhadresh Bundela

Diagnosis of thyroid cancer

The doctor will first run a thyroid ultrasound scan to specifically distinguish between a cyst and a solid lump; the ultrasound will also serve to tell if the thyroid is a goitrous gland within which the lump that has brought the patient to medical attention is just a prominent one of many nodules – the so-called multinodular goitre (which is rarely a malignant condition).

An isotope scan will inform the doctor as to whether the nodule is functioning like a normal thyroid gland, which is very rare indeed in cancers.

Next, the doctor may opt to obtain needle cytology of the lump (were a fine needle is placed within the lump and tissue aspirated for examination under the microscope). If this test demonstrates cancer (carcinoma or lymphoma) then it is a useful test. However, a negative result is less reliable at excluding thyroid carcinoma as some cancers look very similar indeed to the normal thyroid tissue and the sample obtained at cytology is often inadequate to distinguish.

Where doubt exists the patient is usually put up for surgery and a formal hemi-thyroidectomy is performed where the half of the thyroid containing the lump is removed. If it contains differentiated thyroid cancer (vide infra) then a completion thyroidectomy (the removal of the rest of the gland) is performed at a subsequent operation a couple of weeks later.
Stages of thyroid cancer
The most important fact to establish is whether the thyroid carcinoma is confined to the gland. An ultrasound of the thyroid and neck has already probably been done and is an accurate first procedure to delineate the thyroid tumour and identify abnormal lymph nodes. An MRI scan of the neck is also useful, particularly for demonstrating any local extensions of the primary growth.
A CT scan may be useful - especially if the thyroid tumour extends down into the chest but there is an iodine load involved in the contrast that is used in neck CT scanning and this may make difficult subsequent iodine therapy if this is necessary within a few weeks of the CT scan.
The commonest sites of distant spread for thyroid carcinoma are the lungs and the bones – usually in that order. Therefore, a chest x-ray or Ct (with the above caveat over iodine loading) of the thorax and a bone isotope scan are used in staging.
For differentiated carcinoma, the radical surgical operation (vide infra) will often be recommended whatever the staging shows and the operative specimen yields further staging information as to whether the tumour had spread outside the gland or not. By these means, the patient is classified as having intracapsular or extracapsular disease.
The measurement of the serum tumour marker: thyroglobulin is not useful at this time.
In medullary carcinoma cases, the staging is much the same but there is a hormone marker of disease presence in the form the hormone calcitonin (which as has been said above is the normal physiological product of the thyroid C cells). This hormone marker is almost invariably raised in this disease and the level should fall back to normal levels after curative surgery.
By contrast, lymphoma staging is that for any high grade lymphoma (see lymphoma section - but PET scanning and bone marrow exam amongst other tests will be ordered).

Outcomes of thyroid cancer

The vast majority of patients presenting ot the doctor with early, differentiated thyroid cancer will be cured. For example, the young woman with early papillary cancer has a greater than 90% chance of cure, but it is important that the algorithm of care outlined above is followed.
Similarly the chance of cure is good with modern therapy for thyroid lymphoma.
Unfortunately, the chance of surviving undifferentiated thyroid cancer is very much smaller and, despite the therapies outlined above, the majority of these patients die of their disease within one year.
Patients with medullary thyroid cancer have an overall 50% survival to 10 years and those with early stage disease and who have curative surgery, with the disappearance of rasied serum calcitonin, are those who are likely to be in the cured cohort.