Thyroid nodule diagnostic study of choice

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2]

Diagnostic criteria

There is no definite diagnostic criteria for thyroid nodule. Different diagnostic methods can be used to diagnose thyroid nodules, based on their specific properties. The primary evaluation method that should be used in the thyroid patients is thyroid ultrasound. Ultrasound diagnosis of malignant thyroid nodules if done based on marked hypoechogenicity, microcalcification and mixed central/peripheral or central Doppler colour flow pattern has sensitivity of 100 % and a specificity of 76 % were obtained in detecting malignant nodules using this criteria.PMC3781256

The malignancy diagnosis of thyroid nodules is based on cytology. Cytology is the primary determinant in thyroid nodule management, include thyroidectomy indication. After a suspicious to thyroid malignancy based on ultrasound features, fine needle aspiration biopsy (FNAB) is the most appropriate method for further evaluation. Overall sensitivity and specificity of the FNAB technique have been reported to be 83% and 92% respectively.PMC3416902

• Thyroid function should be assessed in all patients with thyroid nodules.
• Thyroid ultrasound should be performed in all patients with a suspected thyroid nodule or nodular goiter on physical examination or with nodules incidentally noted on other imaging studies
• Subsequent evaluation is based upon the TSH level and sonographic features of the nodule(s)
• Thyroid scintigraphy is used to determine the functional status of a nodule.
• Scintigraphy utilizes one of the radioisotopes of iodine (usually 123-I) or technetium-99m pertechnetate. If available, radioiodine scanning is preferred.

Ultrasound indicating critera

• Suspected thyroid nodule
• Nodular goiter
• Radiographic abnormality
  • Nodule found incidentally on computed tomography (CT) or magnetic resonance imaging (MRI)
  • Thyroidal uptake on 18FDG-PET scan

Diagnostic approach

Abbreviations: TSH: Thyroid stimulating hormone, FNA: Fine needle aspiration, FLUS: Follicular lesion of undetermined significance, AUS: Atypia of undetermined significance.

Thyroid nodule found clinically or incidentally                                                                                                                               TSH                                                                                                                                                                                                                                           Normal or elevated                                   Subnormal                                                                                                                                     Radionuclide thyroid scan                                                                                                                                                                   Nodule not up taking the radionuclide Cold nodule Nodule is non-functional               Nodule up taking the radionuclide Hot nodule Nodule is functional                                                                                                                                         Ultrasound evaluation               Check thyroid hormones Free T4 and T3 check                                                                                                                                                                                                                                                                         Meets the criteria           Doesn't meet criteria       Normal Subclinical hypothyroidism   Elevated Thyroid adenoma Hyperthyroidism                                                                                                                           FNA                                   Treat hyperthyroidism                                                                             Monitoring                                                                                                                                                                                                                                                                                                                                                                                                                                     Follicular neoplasm               FLUS     AUS     Benign     Suspicious for malignancy     Papillary thyroid carcinoma   Nondiagnostic                                                                                                                                                       Repeat Ultrasound every 1-2 year If growth more>20% or suspicious ultrasound results, consider FNA again                           Repeat FNA with ultrasound guidance                                                                 Repeat FNA in 2-3 months                                 Total thyroidectomy                                                                                                                                                         AUS FLUS               Benign                                                                                                                                                                                                                                                                                                                                                               Cold, non-functional nodule     Hot, functional, benign nodule                                                                                                                                                                                     Thyroid lobectomy considering ultrasound results AND Molecular diagnostic testing *Gene expression classifier * Mutational analysis                                                                                                                                                                                                                                                                           Suspicious to malignancy               Benign                                                                                                                                                                                   Lobectomy OR Total thyroidectomy based on the ultrasound evaluation