The incidence of palpable (able to be felt) thyroid nodules is 5 percent. Five to 20 percent of patients with thyroid nodules will have cancer.
The patient should undergo a good history and physical examination, followed by a fine-needle aspiration biopsy.
Features suggestive of a cancerous thyroid nodule include:
- Age – Benign thyroid disease is more common in middle-aged individuals and thyroid cancer is more prevalent among children and the elderly.
- Sex (male) – Benign thyroid disease is more common in women but thyroid cancer is more common in men.
- Presence of distant metastasis of unknown primary origin (especially lung metastasis).
- Vocal cord paralysis resulting in hoarseness.
- History of radiation to the neck – previously used for acne; enlarged tonsils, adenoids, or thymus; or skin infections Tumors associated with a history of radiation treatment are often multifocal (occurring in more than one location) papillary cancer. There has been a 30-fold increase in the incidence of thyroid cancer in the areas surrounding the Chernobyl nuclear accident of 1986 (areas of Belarus, the Ukraine and Russia).
- Rapid growth or sudden change in the size of the nodule.
- Residence of the individual –patients in areas without iodized salt are more likely to have benign thyroid disease (goiter).
- Pressure effects (difficulty swallowing or breathing)
The following may be signs of cancer:
- Hard, non movable nodule.
- Presence of cervical (in the neck region) lymph nodes that can be felt.
Fine Needle Aspiration Biopsy
The accuracy of this text exceeds 90 percent (1 percent false positive, 5 percent false negative). It is done with a small (22 or 25 gouge) needle. The results are interpreted as malignant, suspicious, benign or inadequate.
- Malignant (5%) – Papillary cancer, medullary cancer, anaplastic cancer or lymphoma.
- Suspicious (15%) – Follicular neoplasm, Hurthle cell lesion. Most of these patients are recommended to have surgery because these lesions can not be determined to be benign or cancerous based on aspiration biopsy.
- Benign (65%) – Colloid goiter, colloid cyst, thyroiditis. These patients are usually observed. Suppressive therapy with thyroid hormone is sometimes used in an attempt to suppress the growth of the nodule or decrease the size of a goiter.
- Inadequate (15%) – Technical problems (inadequate number of cells aspirated), degenerative nodule, hemorrhagic cyst. These studies are usually repeated.
Tests should be performed for levels of TSH and TT4 (most patients with thyroid nodules have normal thyroid hormone levels). Calcitonin (another hormone) levels should be checked if the patient has a family history of thyroid cancer or multiple endocrine neoplasia (MEN).
Other tests include:
- Thyroid ultrasound – Delineates between a solid mass and a cystic mass and confirms that a solitary nodule is not a dominant nodule in a multi-nodular goiter. Fifteen percent of solid nodules are cancerous while 5 percent of cystic nodules are cancerous.
- Thyroid scan – Uses radioactivity to determine if a thyroid nodule is producing thyroid hormone. Cold nodules reflect non-functioning thyroid nodules with an incidence of cancer of 15-20 percent, while hot nodules reflect functioning thyroid tissue with an incidence of cancer of 4 percent.
- CT scan – Not generally recommended for the evaluation of thyroid masses. The test may be useful in large masses to evaluate for extension under the breastbone or to evaluate for extension into other structures by large tumors.
- MRI – Rarely used for the evaluation of thyroid masses, but it often finds incidental thyroid masses when done for other purposes.