Definition• A discrete swelling in an otherwise impalpable gland is termed solitary thyroid nodule.
• Prevalence - 3-4% of adult population.• Female : Male – 4:1• Importance of STN lies in the risk of malignancy compared with other thyroid swellings. (10 –15% of STN are malignant.)
CONDITIONS PRESENTING AS SOLITARY THYROID NODULE• Dominant nodule of a multinodular goitre.• Thyroid adenoma• Thyroid cyst• Thyroid carcinoma• Localised form of thyroiditis,colloid goitre
Work up of a STN-History Age and gender- Children (Child with a thyroid nodule – 50% chance of it being malignant ) - Men > 50yrs Exposure to radiation for Hodgkin’s / Ca Breast 35yrs after exposure, 7-10% of exposed patients. 100 Rads- Thyroid nodules Thyroid carcinoma >2000 Rads - Prevent thyroid neoplasm (Thyroid gland destroyed) Rapid nodule growth Pain, Hoarseness, Compressive symptoms
History-Contd.• History for specific endocrine disorders-medullary carcinoma,MEN type2• Family h/o thyroid carcinoma
Examination• Firm, irregular texture with fixation.• Enlarged cervical nodes – Papillary cancer
Lab. Evaluation• Thyroid function test ( T3,T4,TSH )- To identify patients with unsuspected hyperthyroid states and dictate appropriate workup.• Serum calcitonin level-Medullary carcinoma is strongly suspected.• Detection of thyroid autoantibodies in patients with toxic features.(anti microsomal and anti thyroglobulin antibodies)
Ultrasound• Nature of the swelling (Solid or cystic) –cystic lesions are usually but not always benign.• To detect nodules of a MNG which are not clinically palpable.• To detect lymph nodes.• Follow up of patients who are managed conservatively to detect increased volume of a suspicious lesion.
Thyroid scan• Using Iodine131 or Technetium-pertechnetate 99m.• On scanning swellings are categorised as hot (overactive),warm(active) or cold(underactive)• Not useful in distinguishing benign and malignant lesions since majority of cold nodules are benign (80%) and some warm nodules are malignant (5%)• Only indication is in patients with toxic features to differentiate Toxic adenoma (rest of the gland is suppressed) from toxic MNG.
FNAC• Single most useful investigation which can detect most of the conditions.• A specimen is considered adequate if at least six properly prepared smears contain 15-20 groups of well preserved clumps of follicular epithelium.• Can diagnose colloid nodules,thyroiditis,papillary carcinoma,medullary carcinoma,anaplastic carcinoma and lymphoma.• Cannot distinguish between a follicular adenoma and carcinoma.• Follicular cells in FNAC - 6-20% chance of malignancy.• Sensitivity –89%
• Specificity-91%.• False negative rate-1-6%. Hence benign nodules diagnosed by FNAC should be followed sequentially with ultrasound to make sure the characteristics do not change.• FNAC results – benign,suspicious or malignant.• Suspicious lesions increased incidence of malignancy.
Benign epithelial cells, colloid, andoccasional macrophages, typical of a "colloid nodule".
Epithelial cells in a follicular arrangementsuggesting adenoma, but which could be from a follicular carcinoma
Hashimotos thyroiditis. A, Group of Hürthle cells, with large cytoplasm and prominent nuclei, surrounded by a teratogeneous population of lymphocytes. B,Hypercellular aspirate with lymphocytes and Hürthle cells.
Epithelial cells in a papillary formation from apapillary thyroid carcinoma. Nuclear grooves are also apparent.
Treatment• FNAC suggestive of colloid nodule – if not otherwise suspicious can be followed up (USG every 6 months to document stability of nodule size)• Thyroid suppression not superior to observation in these patients and risk of osteoporosis is high if thyroid hormone suppression is given to postmenopausal females.
Indications for surgery in STN• Neoplasia :FNAC positive or clinically suspicious-age,male sex,hard texture,fixity,recurrent laryngeal nerve palsy,lymphadenopathy,recurrent cyst• Toxic adenoma• Pressure symptoms• Cosmesis
• Toxic adenoma – Radioiodine and surgery (lobectomy) are equally effective.• FNAC shows follicular cells surgery is indicated(6-20% chance of malignancy).Type of surgery :• Hemithyroidectomy +/- intraop frozen section for suspicious lesions• Near total thyroidectomy if FNAC is suggestive of malignancy.• Subtotal thyroidectomy if STN is a dominant nodule of MNG.
Thyroid cysts• 15-20% of thyroid lesions are cystic lesions• Usually benign and result from an ischemic episode leading to tissue necrosis and liquefaction of a nodule.• About 25% of papillary thyroid carcinomas undergo necrosis and appear partially cystic by USG.• Presence of solid areas within cyst suggest malignancy.
Treatment• Aspiration of cyst is usually curativeIndications for surgery :• Recurrent cyst• Malignant cytology in cyst fluid• Hemorrhagic fluid• Residual swelling after aspiration• Large cyst (size >4cm)