• Clinical science

Thyroid nodules


Thyroid nodules are abnormal growths within the thyroid gland. They are present in approx. 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's thyroiditis being the most common causes. Approx. 5% of thyroid nodules are malignant, with papillary carcinoma being the most common. Thyroid hormone assay is the best initial test in the evaluation of thyroid nodules. Thyroid ultrasonography can detect features suspicious of malignancy in a nodule and the diagnosis can be confirmed on ultrasound-guided fine needle aspiration cytology. Radioiodine uptake scan (thyroid scintigraphy) is used to evaluate nodules in patients with hyperthyroidism, to localize the autonomously functioning tissue. Based on their iodine uptake on radioiodine scans, thyroid nodules may be autonomous/hot (increased uptake) or non-functional/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, fine needle aspiration for thyroid cysts, and observation for small, benign nodules.


  • Sex: > (4:1)
  • Incidence: increases with age
  • 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.


Benign thyroid nodules (∼ 95% of cases)

Malignant thyroid nodules (∼ 5% of cases)


Diagnostic steps for a solitary thyroid nodule

  • Nodule revealed during physical examination or incidentally on imaging
  • Initial tests: thyroid ultrasound and TSH levels
  • Sonographic criteria for fine-needle aspiration (FNA)
    • Solid nodule with suspicious appearance (e.g., oval shape, irregular border, calcifications) that are ≥ 1 cm in diameter
    • Nodules ≤ 1 cm in patients with risk factors for malignancy (see “Etiology” above)
    • Large thyroid nodules (≥ 1.5–2 cm), even if they appear benign

Malignancy is rare in hyperfunctioning (hot) nodules!


Follicular adenoma


Toxic adenoma


Toxic multinodular goiter


Thyroid cysts

  • Classification
    • 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.
  • Etiology
  • Clinical features
    • 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
  • Treatment


  • 1. Welker MJ, Orlov D. Thyroid Nodules. Am Fam Physician. 2003; 67(3): pp. 559–567. url: http://www.aafp.org/afp/2003/0201/p559.html.
  • 2. Dean DS, Gharib H. Epidemiology of thyroid nodules. Best Pract Res Clin Endocrinol Metab. 2008; 22(6): pp. 901–911. doi: 10.1016/j.beem.2008.09.019.
  • 3. Ross DS. Diagnostic approach to and treatment of thyroid nodules. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/diagnostic-approach-to-and-treatment-of-thyroid-nodules. Last updated January 22, 2016. Accessed February 20, 2017.
  • 4. Neki NS, Kazal HS. Solitary Thyroid Nodule – An Insight. JIACM. 2006; 7(4): pp. 328–333. url: http://medind.nic.in/jac/t06/i4/jact06i4p328.pdf.
  • 5. Kasper DL, Fauci AS, Hauser SL, Longo DL, Lameson JL, Loscalzo J. Harrison's Principles of Internal Medicine. New York, NY: McGraw-Hill Education; 2015.
  • 6. Medeiros-Neto G. Multinodular Goiter. url: https://www.ncbi.nlm.nih.gov/books/NBK285569/ Accessed July 13, 2018.
  • 7. Orlander PR. Toxic Nodular Goiter. In: Toxic Nodular Goiter. New York, NY: WebMD. http://emedicine.medscape.com/article/120497-overview. Updated October 14, 2016. Accessed February 20, 2017.
  • 8. Goljan EF. Rapid Review Pathology. Philadelphia, PA: Elsevier Saunders; 2018.
  • 9. Ross DS. Treatment of Toxic Adenoma and Toxic Multinodular Goiter. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/treatment-of-toxic-adenoma-and-toxic-multinodular-goiter. Last updated June 21, 2017. Accessed November 17, 2018.
  • 10. Islam S. Thyroid Gland - Hyperplasia / Goiter / Toxic Multinodular Goiter. http://www.pathologyoutlines.com/topic/thyroidtoxicmultinodulargoiter.html. Updated January 24, 2017. Accessed November 17, 2018.
  • 11. Ramnani D. Multinodular Goiter. https://www.webpathology.com/image.asp?case=260&n=11. Updated October 23, 2018. Accessed November 17, 2018.
  • 12. Williams NS, Bulstrode C, O'Connell PR. Bailey & Love's Short Practice of Surgery. Boca Raton, FL : CRC Press; 2013.
  • 13. Ross DS. Cystic thyroid nodules. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/cystic-thyroid-nodules?source=see_link§ionName=MANAGEMENT&anchor=H14#H14. Last updated August 20, 2015. Accessed February 20, 2017.
  • 14. 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): pp. 341–346. doi: 10.1089/thy.2008.0250.
  • 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): pp. 1–133. doi: 10.1089/thy.2015.0020.
  • 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): pp. 1343–1421. doi: 10.1089/thy.2016.0229.
  • 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.
  • 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): pp. 587–595. doi: 10.1016/j.jacr.2017.01.046.
  • 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): pp. e21–e93. doi: 10.1097/sla.0000000000003580.
  • 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): pp. 622–39. doi: 10.4158/EP161208.GL.
  • Gharib H, Papini E. Thyroid nodules: clinical importance, assessment, and treatment. Endocrinol Metab Clin North Am. 2007; 36(3): pp. 707–35, vi. doi: 10.1016/j.ecl.2007.04.009.
  • 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): pp. 1278–84. doi: 10.1007/s00268-008-9566-0.
  • 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): pp. 1009–1017. doi: 10.1016/j.mayocp.2018.05.020.
last updated 11/16/2020
{{uncollapseSections(['Nic-7X0', '5iciHX0', 'nic7HX0', 'licv7X0', 'IicYGX0', 'kicm7X0', 'OicI7X0', 'VQcGEX0'])}}