Evaluation of thyroid mass

Thyroid parenchymal expansion can result from diffuse enlargement or infiltration of the thyroid gland or from the presence of one or more thyroid nodules.

A thyroid nodule is a discrete lesion distinct from the surrounding thyroid parenchyma. Enlargement of other nearby anatomic structures, such as the parathyroid glands or regional lymph nodes, as well as branchial cleft and thyroglossal duct cysts, may sometimes be confused with thyroid nodules. Thyroid nodules may be palpable at presentation or may be incidentally detected during an imaging procedure (40% are self-identified, 30% are physician-identified, and 30% are incidentally discovered on imaging).[1]Mevawalla N, McMullen T, Sidhu S, et al. Presentation of clinically solitary thyroid nodules in surgical patients. Thyroid. 2011 Jan;21(1):55-9. http://www.ncbi.nlm.nih.gov/pubmed/20954812?tool=bestpractice.com

Incidental detection, in addition to the use of thyroid ultrasonography for surveillance, is thought to be behind an increased reported incidence of thyroid cancers throughout the industrialized world. Neck ultrasonography performed for other indications detects thyroid nodules in more than 20% of the population. Incidental nodules are more common in female patients.[2]Al Shayeb M, Varma SR, El Kaseh A, et al. Incidental thyroid nodules an ultrasound screening of the neck region: prevalence & risk factors. Clin Pract. 2018;15(5):873-9. https://dx.doi.org/10.4172/clinical-practice.1000420 [3]Rad MP, Zakavi SR, Layegh P, et al. Incidental thyroid abnormalities on carotid color Doppler ultrasound: frequency and clinical significance. J Med Ultrasound. 2015 Mar;23(1):25-8. https://doi.org/10.1016/j.jmu.2014.04.005 Autopsy studies detect nodules in over half of the general population by the fifth or sixth decades of life.[4]Mortensen JD, Woolner LB, Bennett WA. Gross and microscopic findings in clinically normal thyroid glands. J Clin Endocrinol Metab. 1955 Oct;15(10):1270-80. https://www.doi.org/10.1210/jcem-15-10-1270 http://www.ncbi.nlm.nih.gov/pubmed/13263417?tool=bestpractice.com

Most nodules are benign and only 5% to 12% of the nodules detected on ultrasonography are malignant.[5]Papini E, Guglielmi R, Bianchini A, et al. Risk of malignancy in nonpalpable thyroid nodules: predictive value of ultrasound and color-Doppler features. J Clin Endocrinol Metab. 2002 May;87(5):1941-6. https://academic.oup.com/jcem/article/87/5/1941/2846442 http://www.ncbi.nlm.nih.gov/pubmed/11994321?tool=bestpractice.com [6]Nam-Goong IS, Kim HY, Gong G, et al. Ultrasonography-guided fine-needle aspiration of thyroid incidentaloma: correlation with pathological findings. Clin Endocrinol (Oxf). 2004 Jan;60(1):21-8. http://www.ncbi.nlm.nih.gov/pubmed/14678283?tool=bestpractice.com  Most thyroid nodules, including thyroid cancers, are asymptomatic. The clinical conundrum in the evaluation of the thyroid nodule is differentiating a benign from a malignant lesion.

Management of thyroid nodules is based on sonographic characteristics and cytology from fine needle aspiration biopsy (FNA). Molecular biomarkers are being increasingly used to enhance the diagnostic clarity from the FNA in patients with follicular neoplasms (Bethesda IV, using the Bethesda system for reporting thyroid cytopathology) and follicular lesions of unknown significance (Bethesda III). Routine biopsy of lesions <1 cm in greatest diameter should be discouraged.[7]Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2016 Jan;26(1):1-133. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4739132/ http://www.ncbi.nlm.nih.gov/pubmed/26462967?tool=bestpractice.com [Figure caption and citation for the preceding image starts]: The Bethesda system for reporting thyroid cytopathology: recommended diagnostic categories, implied risk of malignancy, and recommended clinical management. Risk percentages depend on rates of atypia and follicular lesion as reported by local pathologists. It is important for surgeons to have a good understanding of the pathologist's rationale and reporting rates of the various Bethesda classified thyroid nodules. Management may depend upon many factors such as size, associated symptoms, and patient anxiety, as well as fine needle aspiration (FNA) interpretationCreated by the BMJ Knowledge Centre; adapted from Bumpous J, Celestre MD, Pribitkin E, et al. Decision making for diagnosis and management: algorithms from experts for molecular testing. Otolaryngol Clin North Am. 2014 Aug;47(4):609-23 [Citation ends].

The concept of risk stratification of patients presenting with thyroid nodules that end in a malignant cytologic diagnosis is key to understanding the management approach for thyroid cancer.[7]Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2016 Jan;26(1):1-133. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4739132/ http://www.ncbi.nlm.nih.gov/pubmed/26462967?tool=bestpractice.com It serves as an objective way of prescribing the extent of surgical resection to patients with thyroid cancer, and has been illustrated based upon an escalating scale of known risks.[Figure caption and citation for the preceding image starts]: Risk of structural disease recurrence in patients without structurally identifiable disease after initial therapy (DTC, differentiated thyroid cancer; ETE, extrathryroidal extension; FTC, follicular thyroid cancer; FV, follicular variant; LN, lymph node; PTMC, papillary thyroid microcarcinoma; PTC, papillary thyroid cancer. *BRAF/TERT status not routinely recommended for initial risk stratification. † Risk percentage estimates are best estimates based upon published literature)Created by the BMJ Knowledge Centre; adapted from Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2016 Jan;26(1):1-133 [Citation ends].

Based upon experience in Japan, there is a movement to offer observation of thyroid nodules (biopsy-proven papillary cancers or ultrasonographically suspicious nodules prior to biopsy) to selected patients pending tumor/neck ultrasound characteristics (e.g., primary tumor size and location within the thyroid), individual circumstance (e.g., willingness to accept surveillance, age, comorbid conditions), and the experience of the multidisciplinary clinical team.[8]Ito Y, Miyauchi A, Oda H. Low-risk papillary microcarcinoma of the thyroid: a review of active surveillance trials. Eur J Surg Oncol. 2018 Mar;44(3):307-15. https://www.ejso.com/article/S0748-7983(17)30370-0/fulltext http://www.ncbi.nlm.nih.gov/pubmed/28343733?tool=bestpractice.com [9]Brito JP, Ito Y, Miyauchi A, et al. A clinical framework to facilitate risk stratification when considering an active surveillance alternative to immediate biopsy and surgery in papillary microcarcinoma. Thyroid. 2016 Jan;26(1):144-9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4842944/ http://www.ncbi.nlm.nih.gov/pubmed/26414743?tool=bestpractice.com [10]Miyauchi A. Active surveillance of low-risk papillary microcarcinoma of the thyroid: Kuma hospital protocols and its outcomes. Video Endocrinology. 14 September 2016 [internet publication]. https://doi.org/10.1089/ve.2016.0073  One way to avoid observing known microcarcinomas is to use restraint in biopsying lesions <1 cm in diameter.