thyroid nodules

What are thyroid nodules according to the summary?

Thyroid nodules are abnormal growths within the thyroid gland. Summary 1

How common are thyroid nodules in the general population (detected vs. palpable)?

Present in approximately 50% of the general population but only palpable in 5-10%. Summary / Epidemiology 2

What percentage of thyroid nodules are benign versus malignant?

Approximately 95% of thyroid nodules are benign, and approximately 5% are malignant. Summary / Etiology 3

What are the most common causes of benign thyroid nodules mentioned in the summary?

Colloid cysts, follicular adenomas, and Hashimoto thyroiditis are the most common causes of benign nodules. Summary / Etiology 4

What is the most common form of malignant thyroid disease presenting as a nodule?

Papillary carcinoma is the most common form of malignant disease presenting as a nodule. Summary / Etiology 5

What is a thyroid incidentaloma?

A thyroid nodule that is discovered during imaging for an unrelated cause. Summary / Definitions 6

What are the initial evaluation steps for all thyroid nodules according to the summary?

The initial evaluation includes a TSH assay and thyroid ultrasound. Summary / Diagnosis 7

What diagnostic test is indicated for thyroid nodules if sonographic signs suggest thyroid cancer?

Fine-needle aspiration cytology (FNAC). Summary / Diagnosis 8

Why does a finding of "follicular neoplasm" on FNAC require further evaluation?

Because cytology cannot reliably distinguish between a benign follicular adenoma and a malignant follicular carcinoma. Summary / Diagnosis 9

When is a radioiodine uptake scan (thyroid scintigraphy) used in evaluating thyroid nodules?

It is used to evaluate nodules in patients with low TSH levels. Summary / Diagnosis 10

How are thyroid nodules categorized based on radioiodine scans, and what does each mean?

Autonomous/hot (increased uptake) or nonfunctional/cold (decreased uptake). Summary / Diagnosis 11

What is the clinical significance of a "cold" nodule on thyroid scintigraphy?

Cold nodules carry a 5-15% risk of malignancy. Summary / Diagnosis 12

What is the treatment approach for thyroid nodules based on, according to the summary?

Treatment depends on the underlying etiology (e.g., surgery for malignant/autonomous nodules, aspiration for cysts, observation for small benign nodules). Summary / Treatment 13

Which sex has a higher prevalence of thyroid nodules?

Females have a higher prevalence than males (4:1 ratio). Epidemiology 14

How does age affect the incidence of thyroid nodules?

Incidence increases with age. Epidemiology 15

What geographic factor increases the prevalence of thyroid nodules?

Prevalence is higher in iodine-deficient regions (inland areas without iodine fortification). Epidemiology 16

What is the most common type of benign thyroid adenoma?

Follicular adenoma is the most common type. Etiology 17

List three types of benign thyroid nodules.

Thyroid adenomas (follicular, Hürthle cell, toxic, papillary), thyroid cysts, dominant nodules of multinodular goiters, or Hashimoto thyroiditis nodules. (Any 3) Etiology 18

List the main types of malignant thyroid nodules.

Thyroid carcinoma, thyroid lymphoma, or metastatic cancer (rare, e.g., from breast/renal). Etiology 19

List three "red flags" related to patient characteristics that increase suspicion for thyroid cancer in a nodule.

Male sex, Age < 14 or > 70 years, history of head/neck radiation, family history of MEN2/differentiated thyroid cancer/Gardner syndrome. (Any 3) Etiology 20

List two "red flags" related to symptoms that increase suspicion for thyroid cancer in a nodule.

Rapid growth of the nodule, or recent onset of persistent hoarseness, dysphagia, or dyspnea. Etiology 21

List two "red flags" on palpation that increase suspicion for thyroid cancer in a nodule.

Firm or hard nodule, fixed nodule, or cervical lymphadenopathy. (Any 2) Etiology 22

What is the general diagnostic approach for evaluating any thyroid nodule?

Evaluate all nodules for malignancy. Initial tests: TSH and thyroid ultrasound. Subsequent: Scintigraphy (if low TSH), FNAC (if indicated by ultrasound). Consider tumor markers if needed. Diagnostics / Approach 23

What do TSH levels indicate about the risk of malignancy in a thyroid nodule?

Elevated TSH is associated with a higher risk of malignancy. Low TSH suggests hyperfunction and prompts scintigraphy. Diagnostics / Initial 24

List three high-risk features on thyroid ultrasound that suggest malignancy.

Solid hypoechoic nodule/component PLUS: irregular margins, taller-than-wide shape, microcalcifications, rim calcifications with extruding tissue, OR extrathyroidal extension. (Any 3 features besides solid/hypoechoic) Diagnostics / Initial 25

List two low-risk or very low-risk features on thyroid ultrasound suggesting a benign nodule.

Isoechoic/hyperechoic solid nodule, cystic nodule with eccentric solid component, partially cystic nodule, or spongiform nodule. (Any 2) Diagnostics / Initial 26

What ultrasound finding is considered definitively benign?

Purely cystic nodules (anechoic) without a solid component. Diagnostics / Initial 27

What is the indication for thyroid scintigraphy in the evaluation of a thyroid nodule?

Thyroid nodule(s) found in a patient with a low TSH level. Diagnostics / Subsequent 28

How are the findings of thyroid scintigraphy interpreted regarding malignancy risk?

Cold (hypofunctioning) nodules require further evaluation (check US for FNAC indications). Hot (hyperfunctioning) nodules are rarely malignant (FNAC not usually needed). Diagnostics / Subsequent 29

What conditions typically present as "hot" nodules on thyroid scintigraphy?

A solitary hot nodule suggests a toxic adenoma. Multiple hot nodules suggest a toxic multinodular goiter. Diagnostics / Subsequent 30

What is the general size threshold for performing FNAC on solid hypoechoic thyroid nodules?

Solid hypoechoic nodules ≥ 1 cm generally warrant FNAC. Diagnostics / Subsequent 31

When might FNAC be considered for solid hypoechoic nodules < 1 cm?

Consider if extrathyroidal growth, cervical lymphadenopathy, symptoms of distant metastases are present, or based on patient preference. Diagnostics / Subsequent 32

What is the Bethesda System used for?

It is used for categorizing the cytopathology findings from a thyroid Fine-Needle Aspiration (FNAC). Diagnostics / Subsequent 33

According to the Bethesda system, what is the management for a "Benign" (Category II) finding on FNAC?

No further immediate diagnostic tests needed. Repeat FNAC or sonography within 1-2 years depending on US features. Consider surgery if size > 4 cm or increases significantly. Diagnostics / Subsequent 34

What is the management approach for Bethesda Category III (AUS/FLUS) on thyroid FNAC?

Options include: Repeat FNAC, molecular testing, surveillance, or thyroid lobectomy with histopathology. Diagnostics / Subsequent 35

What is the management approach for Bethesda Category IV (Follicular Neoplasm) on thyroid FNAC?

Options include: Molecular testing or thyroid lobectomy for definitive histopathological diagnosis (cytology cannot distinguish adenoma from carcinoma). Diagnostics / Subsequent 36

What are the next steps for Bethesda Categories V (Suspicious for Malignancy) and VI (Malignant) on thyroid FNAC?

Proceed with management for thyroid cancer (typically surgery). Diagnostics / Subsequent 37

Can FNAC cytology reliably distinguish between a follicular adenoma and follicular carcinoma?

No, cytology alone cannot distinguish between follicular adenoma and carcinoma. Follicular Adenoma 38

How is a definitive diagnosis of follicular adenoma versus carcinoma made?

Surgical excision (e.g., hemithyroidectomy) with histologic analysis showing absence (adenoma) or presence (carcinoma) of capsular/vascular invasion. Follicular Adenoma 39

What is the treatment for a nodule confirmed as follicular adenoma after excision?

No further treatment is required. Follicular Adenoma 40

What genetic mutation often underlies a toxic adenoma?

Gain-of-function mutations of the TSH receptor gene in a single precursor cell. Toxic Adenoma 41

What are the typical thyroid function test results in a toxic adenoma?

Increased T3 (and often T4) with decreased (suppressed) TSH. Toxic Adenoma 42

What is the characteristic finding on thyroid scintigraphy for a toxic adenoma?

A solitary, hyperfunctioning ("hot") nodule with suppression of radioiodine uptake in the rest of the gland. Toxic Adenoma 43

What are the definitive treatment options for a toxic adenoma?

Hemithyroidectomy/isthmusectomy or Radioactive iodine ablation (RAIA). Less invasive ablation techniques may be considered for non-candidates. Toxic Adenoma 44

What is the underlying pathophysiology leading to a nontoxic multinodular goiter (MNG)?

Chronic iodine deficiency/thyroid dysfunction → ↓ hormone → ↑ TRH → persistent TSH stimulation → hyperplasia of thyroid nodules → nontoxic MNG. Toxic MNG 45

How does a nontoxic multinodular goiter become a toxic multinodular goiter (TMNG)?

Multiple somatic mutations of the TSH receptor occur → autonomous functioning of some nodules → hyperthyroidism (↑ T3/T4 release). Toxic MNG 46

What are the characteristic findings on thyroid scintigraphy for a toxic multinodular goiter?

Increased radioiodine uptake by multiple hyperfunctioning ("hot") nodules, with decreased uptake (suppression) in the rest of the gland/intervening tissue. Cold nodules may coexist. Toxic MNG 47

What are the definitive treatment options for a toxic multinodular goiter?

Total or near-total thyroidectomy or Radioactive iodine ablation (RAIA). Toxic MNG 48

How do simple and complex thyroid cysts differ?

Simple cysts are exclusively fluid-filled. Complex cysts are partly solid and partly cystic and carry a 5-10% risk of malignancy. Thyroid Cysts 49

When is FNAC indicated for thyroid cysts based on ultrasound?

Not recommended for purely cystic nodules. For partly cystic: Low risk (eccentric solid) if ≥ 1.5 cm; Very low risk if ≥ 2 cm. Thyroid Cysts 50

How are symptomatic or large benign thyroid cysts treated?

Options include aspiration with/without ethanol ablation, or surgery if aspiration is ineffective. Thyroid Cysts 51

How does the evaluation of thyroid nodules differ in pregnant patients?

Thyroid scintigraphy and RAIA are contraindicated. FNAC is safe if indicated. Ultrasound is used for follow-up. Special Patient Groups 52

How is suspected/diagnosed thyroid cancer managed during pregnancy?

Surgery is usually postponed until after delivery unless aggressive/advanced; if postponed, consider TSH suppression with levothyroxine. Surgery is relatively safe in the 2nd trimester. Special Patient Groups 53

How does the management of thyroid nodules differ in children compared to adults?

Management is similar, but thyroid nodules in children are more frequently malignant, warranting a high index of suspicion. Special Patient Groups 54