4. Molecular testing - AAES GUIDELINES
Molecular testing examines changes in the somatic profile ion the genetic structure of tissues in order to determine the presence of malignant cells. There are several different approaches in the assessment of thyroid nodules however these are an adjunct to clinical examination and fine needle cytology. If thyroidectomy is preferred for clinical reasons or because of a positive fine needle biopsy then molecular testing is not indicated. Its sole purpose is to avoid unnecessary thyroidectomy for a cytologically indeterminate nodule on cytological grounds where the patient prefers not to have surgery. There are two approaches, the first being molecular testing of a panel of genes which are predictive of malignancy (eg ThyGenX) such that a positive test confirms the need for thyroid surgery, and the second being molecular testing a panel of genes specifically designed to associate with a benign nodule (eg Afirma) such that a negative test obviates the need for surgery. There is still need for clinical validation of these tests with the results dependent upon individual institutional rates of thyroid cancer.
Recommendation 11: When the need for thyroidectomy is unclear after consideration of clinical, imaging, and cytologic features, MT may be considered as a diagnostic adjunct for cytologically indeterminate nodules.
Molecular testing has a very narrow role confined to thyroid nodules with indeterminate cytology. The tests are expensive to perform in Australia and still only provide statistical information as to the likelihood or not of thyroid cancer upon which a decision is made to avoid surgery which might otherwise have been indicated. Best advice as to the need for surgery for a thyroid nodule is still based upon clinical and cytological assessment by an experienced thyroid surgeon or endocrinologist within a centre with its own data available to correctly interpret the results..