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 treatment for Stage III papillary or follicular thyroid cancer?
What is the treatment for Stage III papillary or follicular thyroid cancer?
The current recommendation includes:
- Total thyroidectomy plus removal of involved lymph nodes or other sites of extrathyroid disease
- I-131 ablation following total thyroidectomy if the tumor demonstrates uptake
- External-beam radiation therapy if I-131 uptake is minimal
What is the treatment for Stage IV papillary or follicular thyroid cancer?
What is the treatment for Stage IV papillary or follicular thyroid cancer?
- Surgery: total thyroidectomy and neck dissection as indicated. Treatment of distant metastases is usually not curative but may produce good palliation. Metastases with uptake may be ablated by I-131. External-beam radiation is used for localized lesions that are unresponsive to RAI.
- Resection of limited metastases, especially symptomatic metastases, should be considered when the tumor has no uptake of I-131. Removal of structures that will cause functional deficits (i.e., larynx, pharynx, trachea) should be thoroughly discussed with the patient.
- Patients unresponsive to I-131 should be considered for chemotherapy such as inhibitors of vascular endothelial growth-factor (VEGF) receptors.
What is the role of neck dissection in well-differentiated thyroid cancer?
What is the role of neck dissection in well-differentiated thyroid cancer?
Papillary and medullary thyroid cancers have a high propensity to spread to regional lymph nodes whereas follicular carcinomas rarely do. A careful assessment of the central compartment (zone VI) and lateral neck (zones II-IV) should be done prior to surgery. Elective neck dissection beyond the central compartment is controversial. Some authors advocate routine central compartment dissection for PTC larger than 3 cm. Zone Ib (submandibular gland) is rarely involved by locoregional metastasis and can be preserved in thyroid cancer surgery.
What is multiple endocrine neoplasia (MEN)?
What is multiple endocrine neoplasia (MEN)?
The term multiple endocrine neoplasia (MEN) encompasses several distinct syndromes featuring tumors of endocrine glands, each with its own characteristic pattern.
- MEN type I: pancreas, pituitary, parathyroid adenomas
- MEN type IIa: medullary carcinoma of thyroid, pheochromocytoma, parathyroid hyperplasia
- MEN type IIb: MEN IIa and mucosal neuromas; no parathyroid involvement
What is the staging for Medullary Thyroid cancer (MTC)?
see table
What important characteristics are unique to medullary thyroid cancer?
What important characteristics are unique to medullary thyroid cancer?
- More aggressive than well-differentiated thyroid cancers (PTC and FTC)
- Derive from parafollicular or C-cells and can secrete calcitonin and carcinoembryonic antigen (CEA) as well as prostaglandins, histaminases, and serotonin
- High propensity for invasion into muscle and trachea as well as hematogenous spread to lungs and viscera (50% at presentation)
- RET proto-oncogene mutation at codon 634 results in MEN IIa; codon 918 mutation results in MEN IIb.
- MEN IIb type is the most aggressive. Familial medullary thyroid carcinoma (FMTC) has the best prognosis and MEN IIa has an intermediate prognosis
- Sporadic unifocal lesions: 70%; familial/genetic: 30%
What is the workup for medullary thyroid cancer?
What is the workup for medullary thyroid cancer?
Patients positive for RET mutation should be screened for MEN type II tumors: (i) pheochromocytoma: 24-hr urine catecholamine study and abdominal scan to rule out pheochromocytoma; (ii) parathyroid adenoma: serum calcium and PTH. Family members should have genetic screening for RET proto-oncogene and MEN type II tumors. Imaging should evaluate both locoregional and distant metastasis and include MRI, PET, sestamibi and indium-labeled somatostatin scans.
What is the treatment for medullary thyroid cancer?
What is the treatment for medullary thyroid cancer?
Total thyroidectomy and neck dissection (as needed) with resection of any additional structures involved is recommended. Children with MTC should have total thyroidectomy at age younger than 2 years old. Long-term follow-up with serial serum calcitonin and carcinoembryonic antigen (CEA) levels is recommended.
What is anaplastic thyroid cancer?
What is anaplastic thyroid cancer?
- Extremely aggressive malignancy, usually occurs in older patients
- 80% occur in pre-existing thyroid mass suggesting malignant de-differentiation within existing tumor
- Presents as sudden growth in pre-existing mass associated with pain, hoarseness, dysphagia, and dyspnea
