Tests For Thyroid Cancer

If there are relatives with thyroid cancer, a calcitonin blood level would be a very specific test to monitor for medullary thyroid cancer. Because of this very specific test this type of cancer has now a very good prognosis, because it can be diagnosed early and can be monitored when the tumor has been removed surgically to ensure that the cancer does not reoccur. Should it come back, it would also be known early so that steps can be undertaken to combat it again.

Generally speaking, the principle in diagnosing thyroid cancer is to get a tissue diagnosis and to stage the tumor. The methods used are as follows.

When there is a thyroid nodule (thyroid lump), the doctor would refer you to a specialist who will organize a biopsy of the lump. Usually this is done with a mid-size needle and up to 6 needle biopsies are taken under freezing from all corners of this lump to get a good representation of tissue samples. This material is sent to the pathologist who will analyze these samples under the microscope and provide the treating physician with a tissue diagnosis. Before the biopsy is done the physician may decide to do other tests such as a thyroid ultrasound and/or a thyroid scan (=scintigram). With this scan a radioactive isotope (radioactive tracer substance) is given intravenously and after a period of time a scintigram (picture of the radioactive distribution) is done at the Nuclear Medicine Department of the hospital. This will show the physician whether the tumor is "hot" or "cold". The explanation for the previous scintigram is given here.

Mostly the hot tumor is harmless (histologically benign), taking up the tracer substance. If it is cold, and the ultrasound is showing a solid tumor, there is a high suspicion of a malignant tumor. However, all of these imaging studies are only images. There are false positives and false negatives with this thyroid uptake scan. A study was done to test this: thyroid nodules were classified using scintigrams into"hot" and "cold" depending whether they took up the radioactive marker( uptake=hot). All of the nodules were surgically removed and analyzed histologically. 5.5% of all nodules tested positive on scintigrams (=showed up "hot"). Of these there were still a total of 4%, which were cancerous (these had been labeled as false negatives). On the other hand, 85% of the nodules were"cold" and only 20% of these were malignant.

This shows that the tests have some usefulness indistinguishing between malignant and benign.The real proof, however, remains with the pathologist, as cancer is a tissue diagnosis. Only with a biopsy, which will provide the physician with the diagnosis can a proper therapy be planned (Ref.1 and 2). However, when the diagnosis of thyroid cancer is made, there is one other important step before therapy can be instituted, namely the staging of thyroid cancer (click on "thyroid cancer" and look for this topic).

Home Page

Cancer Overview

Thyroid Cancer

Disclaimer:

This outline is only a teaching aid to patients and should stimulate you to ask the right questions when seeing your doctor. However, the responsibility of treatment stays in the hands of your doctor and you.

References:

1. Cancer: Principles&Practice of Oncology. 5th edition, volume 1. Edited by Vincent T. DeVita, Jr. et al. Lippincott-Raven Publ., Philadelphia,PA, 1997. Thyroid tumors.

2. Cancer: Principles &Practice of Oncology, 4th edition, by V.T. De Vita,Jr.,et. al J.B. LippincottCo.,Philadelphia, 1993.Thyroid tumors.

3. CC Cheung et al. J Clin Endocrinol Metab 2001 May;86(5):2187-2190.

4. F Dede et al. Clin Nucl Med 2001 May;26(5):396-399.

5. S Hermann et al. Int J Cancer 2001 Jun 15;92(6):805-811.

6. I Sturm et al. J Clin Oncol 1999 May;17(5):1364-1374.

7. VL Greenberg et al. Thyroid 2001 Apr;11(4):315-325.

8. K Ohta et al. J Clin Endocrinol Metab 2001May;86(5):2170-2177.

Last Modified: Jan. 2, 2009