- Thyroid nodules are very common, found in 4-7% of people on physical exam and almost 50% on ultrasound, with most people having multiple nodules. Thyroid cancer is found in 5-10% of palpable nodules. - Factors that increase cancer risk include nodule size over 3 cm, male sex, radiation exposure, family history of thyroid cancer, and symptoms of local invasion. Features suggesting benign nodules include a family history of autoimmune disease and benign nodules. - Evaluation involves ultrasound, thyroid function tests, and fine needle aspiration of suspicious nodules, with surgery for nodules found to be malignant or indeterminate

1. Thyroid Nodules

2. Thyroid Nodules Prevalence and incidence Palpable nodules: 4-7 % of the population Incidentally on US: almost 50 %, 75 % multi nodular, 25 % solitary Thyroid cancer: 5-10 % of palpable nodules The main objective of evaluating thyroid nodules is to exclude malignancy

3. Type of thyroid nodules Cyst : simple cyst, mixed cystic-solid Colloid nudule : dominant nodule in MNG Adenoma : Follicular, Hurthle cell, Atypical Thyroiditis : Hashimoto’s, subacute Infection : Granulomatous disease, Abscess Developmental anomalies : unilateral lobe agenesis, cystic hygroma, Dermoid, Teratoma Carcinoma : papillary ( 75 %), follicular ( 5-10 %), medullary ( 5-10 %) , anaplastic ( 5 %), lymphoma ( 5 %), metastatic

4. Factors associated with increase risk for malignant thyroid nodule History (moderate increase risk) Age < 20 or > 60 years Male sex Exposure of RT (especially in childhood) F.Hx of thyroid cancer or polyposis Physical finding (highly increase risk) larger than 3 cm Rapid tumor growth Very firm nodule, irregular surface Fixation to adjacent structure Symptom of local invasion: dysphagia, hoarseness Cervical lymphadenopathy Cold nodule on thyroid scan Solid or complex cyst on US

5. Factors suggesting benign thyroid nodule F.Hx of autoimmune disease (Hashimoto’s thyroiditis) F.Hx of benign thyroid nodule or goiter Presense of thyroid hormone dysfunction, hypothyroid or hyperthyroid Pain or tenderness associated with nodule Soft, smooth, mobile MNG without a predominant nodule Warm nodule on thyroid scan Simple cyst on US

6. Investigation Laboratory evaluation TSH: screening for hyper or hypothyroid T 3, T 4 : when TSH are low normal or high normal Serum antithyroid peroxidase (anti-TPO), antithyroglobulin (anti-Tg) if suspected thyroiditis Imaging study CT, MRI, PET: not cost-effective in initial evaluation of thyroid nodule Ultrasound: characters that increase risk for malignant; ill defined margin, irregular shape, solid echo, hypoechoic , calcification (fine): sensitivity 75 %, specificity 61 % Thyroid isotope scanning : 131 I , 123 I , 99 TC cold nodule ( 84 %): cancer risk 15 % warm nodule ( 10.5 %): cancer risk 9 % hot nodule ( 5.5 %): cancer risk 1 % T hyroxine suppression therapy with US follow up sensitivity 83 %, specificity 33 %

7. US: A solitary hypoechoic nodule at Rt. Lobe thyroid Slide 12 Slide 12

8. Isotope scan : Left: Normal thyroid Right: A cold nodule Lt.lobe thyroid

9. Diagnostic procedure: Fine needle aspiration cytology (FNA) Sensitivity: 70-90 %, specificity 70-90 % False negative result: 3-8 % Reliability depend on: Operator Cytopathologist Type of tumor: follicular neoplasm has 20-30 % false negative rate

10. Thyroid Nodule TSH test Euthyroid Thyrotoxic Thyroid scan FNA Cold nodule Hot nodule 131 I or surgery Benign Suspicious Malignant Inadequate Observe or T 4 - Px Surgery Repeat FNA FU 6-12 M Suggested strategy for the management of thyroid nodules

11. Thyroid incedentalomas Incidence: 30-60 % (Autopsy), 13-50 % (Ultrasound) Size: usually < 1.5 cm Incidence of cancer: < 5 %, mostly papillary CA Thyroid incedentaloma Hx. H+N RT, F.Hx. CA thyroid Positive Negative US guide FNA US finding Cytology Suspected Benign appearance Malignant or (< 1.5 cm) ( > 1.5 cm ) Observe Malignant Benign Surgery Observe

12. Frequency Malignant histology Benign 60-65 % 3-8 % Colloid or nodule goiter Thyroiditis Suspicious 10-15 % 20-30 % Follicular neoplasm Hurthle cell lesion Cellular smear Lymphoma Malignant 3-5 % 95 % Papillary Medullary Anaplastic Inadequate 15 % 5 % Techincal problem Degernerative nodule Hemorrhagic cyst Result of thyroid FNA interpretation

13. Colloid nodule : A: FNA B: Histopathology

14. Hoshimoto’s thyroiditis A: FNA B: Histopathology

15. Papillary carcinoma : A: FNA B: Histopathology

16. A: FNA B: Follicular adenoma C: Follicular carcinoma