J Endocrinol Metab

Journal of Endocrinology and Metabolism, ISSN 1923-2861 print, 1923-287X online, Open Access

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Case Report

Volume 16, Number 1, February 2026, pages 38-43

Disappearing Thyroid Nodules: A Case Report and Review of Evidence

↓ Figure 1. Initial and follow-up thyroid ultrasound images. (a) Initial ultrasound images (anteroposterior and longitudinal axes, respectively). (b) Follow-up ultrasound image after 4 months (anteroposterior axis). *: strap muscles; ♣: left common carotid artery; ♦: left sternocleidomastoid muscle; ♠: left Longus colli muscle; ¶: esophagus.

↓ **Table 1.** Chronology of Events and Clinical Evolution
Time point	Clinical event	Findings
FNA: fine-needle aspiration.
Week 0	Initial presentation	Patient detected left anterior cervical mass 2 weeks prior
Week 2	First consultation	Physical examination, laboratory tests, cervical ultrasound
Month 0-4	Observation period	FNA recommended but patient opted for observation
Month 4	Follow-up visit	Patient reported gradual shrinkage, mass became asymptomatic
Month 4+	Ongoing follow-up	Periodic ultrasound surveillance agreed upon

↓ Table 1. Chronology of Events and Clinical Evolution

Time point

Clinical event

Findings

FNA: fine-needle aspiration.

Week 0

Initial presentation

Patient detected left anterior cervical mass 2 weeks prior

Week 2

First consultation

Physical examination, laboratory tests, cervical ultrasound

Month 0-4

Observation period

FNA recommended but patient opted for observation

Month 4

Follow-up visit

Patient reported gradual shrinkage, mass became asymptomatic

Month 4+

Ongoing follow-up

Periodic ultrasound surveillance agreed upon

↓ **Table 2.** Summary of the Characteristics of Studies Reporting Frequencies of Thyroid Nodule Reduction and Disappearance (Reverse Chronological Order)
Study	Type of study	Inclusion criteria	Nodule dimensions	Follow-up	% reduction/disappearance
FNA: fine-needle aspiration; SD: standard deviation.
Bajuk Studen et al, 2021 [13]	Single-center (Slovenia), retrospective, n = 118 and 203 nodules (mean age 57 years, 91% female)	Non-suspicious nodules (FNA if suspicious image) and without autoimmune thyroid disease	Maximum diameter and volume of the largest nodule (mean (SD)): 12.2 mm (8.2) and 1.4 mL (2.4) Multiple nodules: 47%	5 years	Disappearance: 6.9%
Mohammadi et al, 2019 [14]	Single-center (Canada), retrospective, n = 615 and 733 nodules (mean age 61 years, 86% female)	Benign nodules (FNA)	No dimensions specified	Mean: 3.5 years	Reduction: 28.8%
Bhatia et al, 2016 [15]	Single-center (USA), retrospective, n = 656 (mean age: 50 years, 88% female)	Nodules identified by ultrasound, with FNA and referral for surgery	Diameter (mean (SD)): 24.6 mm (15)	Does not specify time between the ultrasound and the surgery	Disappearance: 2.5%
Durante et al, 2015 [3]	Multicenter (Italy), prospective, n = 992 and 1,567 nodules (mean age: 52 years, 82% women)	Asymptomatic nodules without evidence of malignancy (FNA if diameter > 1 cm and/or image of suspicion), solid or mixed (cystic component < 75%). No autoimmune thyroid disease. Euthyroidism.	Maximum diameter and volume of the largest nodule (mean (SD)): 14.2 mm (8.1) and 1.47 mL (2.81) Multiple nodules: 40%	5 years	Reduction: 13.1%
Choi et al, 2015 [4]	Single-center (South Korea), retrospective, n = 210 and 217 nodules (mean age: 54 years, 70% women)	Nodules with > 50% cystic component and a maximum diameter of > 2 cm Group 1 (n = 59): observation without FNA Group 2 (n = 109): FNA without drainage Group 3 (n = 49): FNA with drainage	Maximum diameter of the largest nodule of group 1 (mean (SD)): 30.9 mm (10.4)	Mean: 1.5 years	Reduction (partial/total collapse): Group 1: 22%/0% Group 2: 22%/4% Group 3: 41%/16%
Krejbjerg et al, 2014 [11]	Population-based (Denmark), prospective, n = 2,465 (618 with nodules, ∼ 40% of 5-10 mm max diameter)	Representative population with baseline and follow-up ultrasound after iodization program	Diameter and volume (median (p25 - p75)): 11.9 mm (11 - 15.9) and 15.9 mL (11.5 - 24.6)	Mean: 11.2 years	Disappearance: 23.8% (especially the solitary ones)
Erdogan et al, 2006 [16]	Single-center (Turkey), retrospective, n = 420 and 531 nodules (mean age: 45 years, 92% women)	Nodules without evidence of malignancy (FNA if diameter > 1 cm) and cystic component < 25%. No autoimmune thyroid disease. Euthyroidism.	Maximum diameter and volume of the largest nodule (mean (SD)): 12.2 mm (8.2) and 1.94 mL (3.94) Multiple nodules: 47%	Mean: 3.3 years	Reduction: 33.1% Disappearance: 4.3%
Rago et al, 2001 [12]	Single-center (Italy), prospective, n = 482, 37 cysts < 1 cm and 27 nodules (mean age 37 years, 53% female)	Thyroid morphology study in healthcare workers	Multiple nodules: 22%	3 years	Disappearance: 27% (cysts < 1 cm) and 0% (other nodules)
Brander et al, 2000 [17]	Single-center (Finland), prospective, n = 57 (34 nodules)	Ultrasound-detected nodules in population-based study	No dimensions specified	Mean: 5.2 years	Reduction or Disappearance: 24%
Kuma et al, 1994 [18]	Single-center (Japan), retrospective, n = 134 (mean age: 44 years, 96% female)	Nodules without surgical criteria with benign baseline FNA in which FNA is subsequently repeated	No dimensions specified Multiple nodules: 10%	9 - 11 years	Disappearance: 33.6% (50% of pure cysts)
Ng et al, 1990 [19]	Single-center (Singapore), retrospective, n = 41 (mean age: 41 years, 83% female)	Single nodules on which FNA was performed		Mean: 5.5 months	Disappearance: 34%

↓ Table 2. Summary of the Characteristics of Studies Reporting Frequencies of Thyroid Nodule Reduction and Disappearance (Reverse Chronological Order)

Study

Type of study

Inclusion criteria

Nodule dimensions

Follow-up

% reduction/disappearance

FNA: fine-needle aspiration; SD: standard deviation.

Bajuk Studen et al, 2021 [13]

Single-center (Slovenia), retrospective, n = 118 and 203 nodules (mean age 57 years, 91% female)

Non-suspicious nodules (FNA if suspicious image) and without autoimmune thyroid disease

Maximum diameter and volume of the largest nodule (mean (SD)): 12.2 mm (8.2) and 1.4 mL (2.4)
Multiple nodules: 47%

5 years

Disappearance: 6.9%

Mohammadi et al, 2019 [14]

Single-center (Canada), retrospective, n = 615 and 733 nodules (mean age 61 years, 86% female)

Benign nodules (FNA)

No dimensions specified

Mean: 3.5 years

Reduction: 28.8%

Bhatia et al, 2016 [15]

Single-center (USA), retrospective, n = 656 (mean age: 50 years, 88% female)

Nodules identified by ultrasound, with FNA and referral for surgery

Diameter (mean (SD)): 24.6 mm (15)

Does not specify time between the ultrasound and the surgery

Disappearance: 2.5%

Durante et al, 2015 [3]

Multicenter (Italy), prospective, n = 992 and 1,567 nodules (mean age: 52 years, 82% women)

Asymptomatic nodules without evidence of malignancy (FNA if diameter > 1 cm and/or image of suspicion), solid or mixed (cystic component < 75%). No autoimmune thyroid disease. Euthyroidism.

Maximum diameter and volume of the largest nodule (mean (SD)): 14.2 mm (8.1) and 1.47 mL (2.81)
Multiple nodules: 40%

5 years

Reduction: 13.1%

Choi et al, 2015 [4]

Single-center (South Korea), retrospective, n = 210 and 217 nodules (mean age: 54 years, 70% women)

Nodules with > 50% cystic component and a maximum diameter of > 2 cm
Group 1 (n = 59): observation without FNA
Group 2 (n = 109): FNA without drainage
Group 3 (n = 49): FNA with drainage

Maximum diameter of the largest nodule of group 1 (mean (SD)): 30.9 mm (10.4)

Mean: 1.5 years

Reduction (partial/total collapse):
Group 1: 22%/0%
Group 2: 22%/4%
Group 3: 41%/16%

Krejbjerg et al, 2014 [11]

Population-based (Denmark), prospective, n = 2,465 (618 with nodules, ∼ 40% of 5-10 mm max diameter)

Representative population with baseline and follow-up ultrasound after iodization program

Diameter and volume (median (p25 - p75)): 11.9 mm (11 - 15.9) and 15.9 mL (11.5 - 24.6)

Mean: 11.2 years

Disappearance: 23.8% (especially the solitary ones)

Erdogan et al, 2006 [16]

Single-center (Turkey), retrospective, n = 420 and 531 nodules (mean age: 45 years, 92% women)

Nodules without evidence of malignancy (FNA if diameter > 1 cm) and cystic component < 25%. No autoimmune thyroid disease. Euthyroidism.

Maximum diameter and volume of the largest nodule (mean (SD)): 12.2 mm (8.2) and 1.94 mL (3.94)
Multiple nodules: 47%

Mean: 3.3 years

Reduction: 33.1%
Disappearance: 4.3%

Rago et al, 2001 [12]

Single-center (Italy), prospective, n = 482, 37 cysts < 1 cm and 27 nodules (mean age 37 years, 53% female)

Thyroid morphology study in healthcare workers

Multiple nodules: 22%

3 years

Disappearance: 27% (cysts < 1 cm) and 0% (other nodules)

Brander et al, 2000 [17]

Single-center (Finland), prospective, n = 57 (34 nodules)

Ultrasound-detected nodules in population-based study

No dimensions specified

Mean: 5.2 years

Reduction or Disappearance: 24%

Kuma et al, 1994 [18]

Single-center (Japan), retrospective, n = 134 (mean age: 44 years, 96% female)

Nodules without surgical criteria with benign baseline FNA in which FNA is subsequently repeated

No dimensions specified
Multiple nodules: 10%

9 - 11 years

Disappearance: 33.6% (50% of pure cysts)

Ng et al, 1990 [19]

Single-center (Singapore), retrospective, n = 41 (mean age: 41 years, 83% female)

Single nodules on which FNA was performed

Mean: 5.5 months

Disappearance: 34%