Thyroid nodules

Last updated: September 18, 2022

Summarytoggle arrow icon

Thyroid nodules are abnormal growths within the thyroid gland. They are present in approximately 50% of the general population but only palpable in 5–10% of the population. They are more common in women, especially in iodine-deficient regions, and their incidence increases with age. Thyroid nodules are the clinical manifestation of various underlying thyroid diseases. The majority of them are benign (∼ 95%), with colloid cysts, follicular adenomas, and Hashimoto thyroiditis being the most common causes. Approximately 5% of thyroid nodules are malignant, with papillary carcinoma being the most common form of malignant disease. A thyroid incidentaloma is a nodule that is discovered during imaging for an unrelated cause and should be evaluated in the same way as other nodules. The initial evaluation of all thyroid nodules includes a TSH assay and thyroid ultrasound. Sonographic signs of thyroid cancer should be further evaluated with fine-needle aspiration cytology (FNAC). Identification of a follicular neoplasm on FNAC necessitates further diagnostic evaluation with either molecular testing or surgical excision and histopathology because cytology cannot reliably distinguish between a follicular adenoma and a follicular carcinoma. A radioiodine uptake scan (thyroid scintigraphy) is used to evaluate nodules in patients with low TSH levels. Based on their iodine uptake on radioiodine scans, thyroid nodules can be categorized as autonomous/hot (increased uptake) or nonfunctional/cold (decreased uptake). The most common hot nodules are toxic adenomas and dominant nodules of toxic multinodular goiters. With a 5–15% risk of malignancy, cold nodules are clinically significant. Treatment depends on the underlying etiology and includes, e.g., surgery (thyroidectomy) for malignant and autonomous nodules, aspiration for thyroid cysts, and observation for small, benign nodules.

Epidemiologytoggle arrow icon

  • Sex: > (4:1)
  • Incidence: increases with age [1]
  • Geographic distribution: most common in inland regions without iodine fortification programs, where iodine content in food and water is low


Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

Benign thyroid nodules (∼ 95% of cases)

Malignant thyroid nodules (∼ 5% of cases)

In addition to red flags for thyroid cancer, a solid nodule on thyroid ultrasound or a cold nodule on thyroid scintigraphy should raise suspicion for thyroid cancer.

Diagnosticstoggle arrow icon

Approach [3][6][7]

Initial evaluation [3][6][9]

Sonographic evaluation of thyroid nodules [6]
Overview Risk pattern Ultrasound findings
Sonographic signs of thyroid malignancy High risk
  • Solid hypoechoic nodule or solid hypoechoic component with at least one of the following:
    • Irregular margins
    • Taller-than-wide shape
    • Microcalcifications
    • Rim calcifications with extruding tissue
    • Extrathyroidal extension
Intermediate risk
  • Solid hypoechoic nodule without high-risk features
Sonographic signs of benign thyroid nodules Low risk
  • Isoechoic or hyperechoic solid nodule
  • Cystic nodule with eccentric solid component
Very low risk
  • Partially cystic nodule
  • Spongiform nodule
  • Cystic nodules (anechoic) without solid component

Thyroid ultrasound is not a screening test for the general population. It is indicated as initial test for patients with palpable thyroid nodules or clinical suspicion for thyroid malignancy. [3]

Solid, hypoechoic nodules with irregular margins, microcalcifications, taller-than-wide shape, extrathyroidal growth, and/or cervical lymphadenopathy should raise suspicion for malignancy and require further evaluation with FNAC.

Subsequent evaluation

Thyroid scintigraphy [3][10]

Malignancy is rare in hyperfunctioning (hot) nodules. [11]

Fine-needle aspiration cytology (FNAC) [3][6]

If thyroid scintigraphy is performed, sonographic features of thyroid nodules should be used to determine which cold nodules require FNAC. Cold nodules with a benign appearance on thyroid ultrasound do not routinely require FNAC.

Bethesda system for thyroid cytopathology [13]

Diagnostic category

Management [6]
I: Nondiagnostic or unsatisfactory
II: Benign
  • No further immediate diagnostic tests required
  • Repeat FNAC or sonography within 1– 2 years depending on sonographic features.
    • After two benign findings, no further follow-up is needed.
    • If there is an increase in size or the size is > 4 cm: Consider surgical removal for symptom relief.
III: Atypia or follicular lesion of undetermined significance
  • Consider any of the following:
IV: Follicular neoplasm or suspicious for follicular neoplasm
V: Suspicious for malignancy
VI: Malignant

Follicular adenomatoggle arrow icon


Clinical features [9]

Diagnostics [6]

Follicular adenoma is a histopathological diagnosis. Cytology alone cannot distinguish between adenoma and carcinoma. For the initial workup, see “Diagnostic approach to thyroid nodules”.

Treatment [9]

Toxic adenomatoggle arrow icon


  • Third most common cause of hyperthyroidism
  • Sex: > [15]
  • Age: more common in individuals 30–50 years of age


Clinical features

Diagnostics [16]

For the initial workup, see “Diagnostic approach to thyroid nodules.”

Treatment [10]

Toxic multinodular goitertoggle arrow icon

Epidemiology [16]

  • Sex: >
  • Age: often > 60 years
  • Second most common cause of hyperthyroidism
  • Develops in 10% of patients with a long-standing nodular goiter
  • More prevalent in iodine-deficient regions


Clinical features [16]

Diagnostics [16]

For the initial workup of a nodular goiter, see “Diagnostic approach to thyroid nodules.”

Treatment [10][17]

Thyroid cyststoggle arrow icon

Classification and etiology [7]

  • Simple cysts are exclusively fluid-filled nodules lined by benign epithelial cells.
  • Complex cysts are partly solid and partly cystic and carry a 5–10% risk of malignancy. [19]
  • Most commonly due to cystic degeneration of thyroid tissue or involution of an adenoma

Clinical features

  • Palpable thyroid nodule
  • Hemorrhage into a cyst → pain and rapid enlargement of the nodule
  • A large cyst or extensive hemorrhage can cause compression symptoms (e.g., hoarseness, dysphagia).

Diagnostics [6]

The initial workup is the same as that for other thyroid nodules (see “Diagnostic approach to thyroid nodules”).

  • Thyroid function tests: typically normal
  • Thyroid ultrasound
    • Cystic components appear anechoic.
    • May be mixed with solid components
  • FNAC: based on FNAC indications for thyroid nodules [6][20]
    • Purely cystic nodule: diagnostic FNAC not recommended
    • Partly cystic nodule
      • Low risk pattern (eccentric solid component): FNAC if size is ≥ 1.5 cm
      • Very low risk pattern: Consider FNAC if size is ≥ 2 cm.

Treatment [6]

Special patient groupstoggle arrow icon

Pregnant patients [3]

Management of thyroid nodules in pregnancy is similar to those in nonpregnant patients, except for the following points.

Children [3]

  • Management is similar to that of thyroid nodules in adults.
  • Thyroid nodules in children are more frequently malignant.

Referencestoggle arrow icon

  1. Gharib H, Papini E. Thyroid nodules: clinical importance, assessment, and treatment. Endocrinol Metab Clin North Am. 2007; 36 (3): p.707-35, vi.doi: 10.1016/j.ecl.2007.04.009 . | Open in Read by QxMD
  2. Lee MJ, K, Kim EK, Kwak JY, Kim MJ. Partially Cystic Thyroid Nodules on Ultrasound: Probability of Malignancy and Sonographic Differentiation. Thyroid. 2009; 19 (4): p.341-346.doi: 10.1089/thy.2008.0250 . | Open in Read by QxMD
  3. Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016; 26 (1): p.1-133.doi: 10.1089/thy.2015.0020 . | Open in Read by QxMD
  4. Tessler FN, Middleton WD, Grant EG, et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. J Am Coll Radiol. 2017; 14 (5): p.587-595.doi: 10.1016/j.jacr.2017.01.046 . | Open in Read by QxMD
  5. Iñiguez-Ariza NM, Lee RA, Singh-Ospina NM, Stan MN, Castro MR. Ethanol Ablation for the Treatment of Cystic and Predominantly Cystic Thyroid Nodules.. Mayo Clin Proc. 2018; 93 (8): p.1009-1017.doi: 10.1016/j.mayocp.2018.05.020 . | Open in Read by QxMD
  6. $Multinodular Goiter.
  7. Sharma A, Stan MN. Thyrotoxicosis: Diagnosis and Management. Mayo Clin Proc. 2019; 94 (6): p.1048-1064.doi: 10.1016/j.mayocp.2018.10.011 . | Open in Read by QxMD
  8. Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. Thyroid. 2016; 26 (10): p.1343-1421.doi: 10.1089/thy.2016.0229 . | Open in Read by QxMD
  9. Porterfield JR Jr, Thompson GB, Farley DR, Grant CS, Richards ML. Evidence-based management of toxic multinodular goiter (Plummer's Disease). World J Surg. 2008; 32 (7): p.1278-84.doi: 10.1007/s00268-008-9566-0 . | Open in Read by QxMD
  10. Patel KN et al. The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Thyroid Disease in Adults. Ann Surg. 2020; 271 (3): p.e21-e93.doi: 10.1097/sla.0000000000003580 . | Open in Read by QxMD
  11. Tarantino L, Francica G, Sordelli I, et al. Percutaneous Ethanol Injection of Hyperfunctioning Thyroid Nodules: Long-Term Follow-Up in 125 Patients. American Journal of Roentgenology. 2008; 190 (3): p.800-808.doi: 10.2214/ajr.07.2668 . | Open in Read by QxMD
  12. Intenzo CM, Depapp AE, Jabbour S, Miller JL, Kim SM, Capuzzi DM. Scintigraphic manifestations of thyrotoxicosis. Radiographics. 2003; 23 (4): p.857-869.doi: 10.1148/rg.234025716 . | Open in Read by QxMD
  13. Gharib H, Papini E, Garber JR, et al. American Association of Clinical Endocrinologists, American College of Endocrinology, and Associazione Medici Endocrinologi Medical Guidelines for clinical practice for the diagnosis and management of thyroid nodules-2016 update. Endocr Pract. 2016; 22 (5): p.622-39.doi: 10.4158/EP161208.GL . | Open in Read by QxMD
  14. Russ G, Leboulleux S, Leenhardt L, Hegedüs L. Thyroid Incidentalomas: Epidemiology, Risk Stratification with Ultrasound and Workup. Eur Thyroid J. 2014; 3 (3): p.154-163.doi: 10.1159/000365289 . | Open in Read by QxMD
  15. Mirfakhraee S, Mathews D, Peng L, Woodruff S, Zigman JM. A solitary hyperfunctioning thyroid nodule harboring thyroid carcinoma: review of the literature. Thyroid Res. 2013; 6 (1): p.7.doi: 10.1186/1756-6614-6-7 . | Open in Read by QxMD
  16. Cibas ES, Ali SZ. The 2017 Bethesda System for Reporting Thyroid Cytopathology.. Thyroid. 2017; 27 (11): p.1341-1346.doi: 10.1089/thy.2017.0500 . | Open in Read by QxMD
  17. Dean DS, Gharib H. Epidemiology of thyroid nodules. Best Pract Res Clin Endocrinol Metab. 2008; 22 (6): p.901-911.doi: 10.1016/j.beem.2008.09.019 . | Open in Read by QxMD
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  20. Welker MJ, Orlov D. Thyroid nodules.. Am Fam Physician. 2003; 67 (3): p.559-66.
  21. McHenry CR, Phitayakorn R. Follicular Adenoma and Carcinoma of the Thyroid Gland. Oncologist. 2011; 16 (5): p.585-593.doi: 10.1634/theoncologist.2010-0405 . | Open in Read by QxMD
  22. Jameson JL, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J. Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2). McGraw-Hill Education / Medical ; 2018

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