15a Disease of the Thyroid Gland Flashcards
What is the incidence of a thyroid nodule?
What is the incidence of a thyroid nodule?
- Clinically palpable nodules occur in 4% to 7% of the population,
- Rate of incidental nodule found on ultrasound is higher (20% to 67% of patients)
- with more than half the thyroids containing more than one nodule.
- Nodules are more common in women (F : M ratio of 4 : 1).
- Thyroid cancer occurs in 5% to 10% of palpable nodules.
What is the workup of a thyroid nodule?
What is the workup of a thyroid nodule?
- Comprehensive history and physical including a visualization of the vocal cords (laryngoscopy)
- Laboratory studies including thyroid function assay and serum calcium
- Ultrasound evaluation of nodule
What features indicate a higher risk of malignancy in the thyroid?
What features indicate a higher risk of malignancy in the thyroid?
- Age <30 years and >60 years
- Male
- Positive family history
- Radiation exposure as child
- Elevated TSH/Hashimoto’s thyroiditis
- Rapid growth
- Pain
- Compressive symptoms
- Hoarseness
- Cervical lymph nodes
What ultrasound features are indications for a fine needle aspiration (FNA)?
What ultrasound features are indications for a fine needle aspiration (FNA)?
- All nodules >1 cm, or smaller if other high-risk features are present (as below)
- Microcalcification
- Irregular margins
- Solid rather than cystic nodule
- Internal vascularity
- Multiple nodules
- Enlarged cervical lymph nodes on the same side of the neck
“I MIS ME”
What is the diagnostic accuracy of FNA cytology?
What is the diagnostic accuracy of FNA cytology?
Accuracy 95%; false negative rate 2.3%; false positive 1.1%
What are the FNA cytopathologic categories of thyroid nodules?
What are the FNA cytopathologic categories of thyroid nodules?
- Benign: 70%
- Malignant: 5%
- Suspicious: 10%
- Indeterminate: 15%
Of suspicious lesions, 10% to 20% will likely be follicular carcinomas on surgical pathology. With follicular lesions, I-123 scan may be helpful. If the lesion is “hot,” it is unlikely to be malignant.
What is the role of molecular testing for thyroid cancer?
What is the role of molecular testing for thyroid cancer?
Molecular testing allows for nodules in the “indeterminate” cytopathologic category (30% of all nodules) to be “ruled in” as cancer or “ruled out” as benign nodules. Proponents argue that this would save unnecessary surgeries and prevent two-surgery approaches (lobectomy followed by completion thyroidectomy).
What molecular tests are currently available for thyroid cancer?
What molecular tests are currently available for thyroid cancer?
- Mutation panel testing: tests for mutations most commonly seen in thyroid cancer including BRAF, RAS, RET/PTC and PAX8/PPARϒrearrangements. When positive, this test “rules in” a likely malignancy with a positive predictive value of 100%. However, 30% of thyroid cancers do not currently have a known mutation.
- Gene expression testing: tests for 142 genes expressed differently between benign and malignant nodules. Test “rules out” nodules as benign and has a negative predictive value greater than 95%. The test is proprietary and expensive ($3,000).
What is the recommended follow-up for a benign thyroid nodule?
What is the recommended follow-up for a benign thyroid nodule?
Most authors recommend serial ultrasounds (every 6 to 12 mos) to look for changes in size or internal characteristics. Any significant changes may warrant a repeat FNA. Cysts that recur after multiple FNAs should be considered for surgical excision to establish a diagnosis. Suppression by exogenous thyroxine is NOT recommended.
What is the differential diagnosis of thyroid cancers?
What is the differential diagnosis of thyroid cancers?
- Papillary carcinoma: 70% to 85%
- Follicular carcinoma: 15% to 20%
- Hurthle cell carcinoma: 3% to 5%
- Medullary carcinoma: 3% to 10%
- Anaplastic carcinoma: <2%
- Insular or poorly differentiated carcinoma: rare
- Other: lymphoma, squamous cell carcinoma, metastases
What is the TMN staging for a well-differentiated thyroid cancer?
see table
What is the staging for well-differentiated thyroid cancers?
see table
What are the clinical prognostic indicators for thyroid cancer?
What are the clinical prognostic indicators for thyroid cancer?
-
AMES: Age; Metastasis; Extent, and Size of primary tumor
- Low risk: age <40 (M) or <50 (F); tumor <4 cm and within thyroid gland
- High risk: Age >41 (M) or >51 (F); extrathryoid invasion; size >5 cm
-
MACIS: Metastasis; Age; Completeness of resection; Invasion; Size of tumor
- High risk: age >40; invasion of thyroid gland; incomplete tumor resection; size >4 cm
What is the difference between total thyroidectomy (TT), near-total thyroidectomy (NT), and sub-total thyroidectomy?
What is the difference between total thyroidectomy (TT), near-total thyroidectomy (NT), and sub-total thyroidectomy?
Total thyroidectomy is the complete removal of all visible thyroid tissue. In near-total thyroidectomy, the surgeon elects to leave a very small amount of thyroid tissue around the parathyroid glands or recurrent laryngeal nerve to reduce morbidity. A sub-total thyroidectomy is ill-defined and results in large amounts of thyroid tissue left behind. A sub-total thyroidectomy is NOT an acceptable surgery for thyroid cancer.
What is the treatment for Stage I and II papillary or follicular thyroid cancer?
What is the treatment for Stage I and II papillary or follicular thyroid cancer?
The treatment for well-differentiated thyroid cancer is a total thyroidectomy. Lobectomy alone results in a higher risk of local recurrence and death, except in some micro PTC <1 cm (see Question # 25). Total thyroidectomy also allows for radioactive iodine (RAI) I-131 thyroid ablation, which can improve the specificity of thyroglobulin assays and allows the detection of persistent disease by total body scanning.
What is the staging for Medullary Thyroid cancer (MTC)?
see table
