Solitary Thyroid Nodule (STN)
A discrete swelling in an otherwise impalpable gland is termed solitary thyroid nodule
- Prevalence: 3-5 % 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.
Types of Solitary Thyroid Nodule (STN):
- Dominant nodule of a multinodular goitre
- Thyroid adenoma
- Thyroid cyst
- Thyroid carcinoma
- Localised form of thyroiditis, colloid goiter
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
- 35 yrs 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 for specific endocrine disorders-medullary carcinoma, MEN type2
- Family h/o thyroid carcinoma
Evaluation of STN:
- 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).
- 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.
- 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.
- MRI, CT (Rarely indicated)
- Only to evaluate retro-sternal extension
- PET scan using FDGF18 (fluorodeoxyglucose F18)
- It can differentiate benign from malignant but highly expensive and can not replace biopsy
- Levothyroxine: (in benign nodule ) to keep TSH below 1 mU/L. It has many side effects, so not recommended.
- Surgery: indicated in
- FNAC positive or clinically suspicious (eldery, male, hard texture, fixed, recurrent laryngeal nerve palsy, lymphadenopathy, recurrent cyst)
- Cosmosis, Toxic nodule, Pressure symptoms
- Methods - Lobectomy + isthemusectomy: In pt with low risk factors & Benign
- Total thyroidectomy: In pt with high risk factors, Benign nodules & Malignant nodules
- Radioiodine: indicated in functioning nodule, contraindicated in pregnancy, lacatation, children. S/E: hypothyroidism, carcinogenic, fetal anomalies in pregnant women.
- Percutaneous ethanol injection, and laser photocoagulation.
According to American Thyroid Association & American Association of Clinical Endocrinology:
- Radionuclide scan is only indicated in:
- suppressed TSH
- if FNAC → follicular neoplasia
- FNAC should be guided by U/S especially if the nodule is partially cystic.
- Benign nodule → Life long Follow-up every year (TSH, neck palpation, FNAC), if functioning : Iodine -131 is TTT of choice, and Surgery is indicated in:
- very large nodule, Partially cystic, young patient, pregnant
- malignant nodule → surgry
- Autoimmune thyroidits → cortison + L-thyroxin
- Infections → control
Dr Rami Hamed Center is one of the leading Dubai thyroid clinic specializes in thyroid surgery.