Thyroid nodules that disappear—a case report on pseudonodules in thyroiditis

Introduction

Patients with thyroid nodules commonly present to clinical attention. The usual work-up includes history-taking, neck examination, thyroid function test, laryngoscopy, ultrasonography of the thyroid gland, and a fine-needle aspiration cytology (FNAC) in nodules suspicious of malignancy. This case report examines pseudonodules arising from thyroiditis in order to raise awareness of this condition, as they can appear moderately suspicious sonographically with the only diagnostic clue being pain and subclinical hyperthyroidism. Recognizing the diagnosis of pseudonodules can lead to expectant management, avoiding unnecessary invasive procedures. We present this case in accordance with the CARE reporting checklist (available at https://aot.amegroups.com/article/view/10.21037/aot-23-39/rc).

Case presentation

A 58-year-old Chinese female in Singapore presented with an episode of acute left anterior neck pain, tenderness and swelling that started spontaneously and lasted a month. This was associated with palpitations but no fever, heat-intolerance, insomnia, diarrhea, loss of weight, dysphagia, dyspnea, or hoarseness. Her only comorbidity was hypertension. Her mother was previously diagnosed with an unspecified cancer in the neck. Within a week, the pain resolved spontaneously but the neck swelling persisted. On examination, a palpable and tender left lower central neck lump that moved with swallowing was present. No cervical lymphadenopathy was palpable. There was no sign of thyrotoxicosis. Flexible laryngoscopy showed normal vocal cord mobility.

Thyroid function test showed that the thyroid stimulating hormone (TSH) was 0.16 mIU/mL (range of normality 0.45–4.5 mIU/mL), free thyroxine (T4) was 16 (range of normality 10 to 16 pmol/L), anti-thyroid peroxidase (TPO) was <5 IU/mL (range of normality 0–50 IU/mL), anti-thyroglobulin (TG) was <10 IU/mL (range of normality 0–100 IU/mL), and TSH receptor antibody (TRAB) was 1.0 IU/L (range of normality 0–1.0 IU/L).

Sonography of the thyroid gland performed 16 days after presentation revealed two right-sided thyroid nodules: a 2.5 cm solid iso-to-hypoechoic nodule with no peripheral vascularity located in the right mid-to-lower pole and a 1.1 cm solid circumscribed heterogeneous hypoechoic nodule without calcifications in the right upper pole. Both were TR4 according to the American College of Radiologist Thyroid Imaging Reporting and Data System (ACR-TIRADS) (1). The left lobe measured 4.0 cm × 1.0 cm × 1.6 cm in size, was heterogenous, without well-defined nodules (Figure 1A-1D).

Figure 1 Sonography of the thyroid gland 1 month after presentation. Grey-scale ultrasound images of the upper pole of the right thyroid lobe in longitudinal (A) and transverse (B) orientations. There is a solid circumscribed heterogeneous hypoechoic nodule without calcifications. It measures 1.0 cm (L) × 1.1 cm (W) × 0.6 cm (H). Grey-scale ultrasound images of the mid to lower poles of the right thyroid lobe in longitudinal (C) and transverse (D) orientations. There is another solid circumscribed heterogeneous hypoechoic nodule without calcifications. It measures 2.5 cm (L) × 1.1 cm (W) × 0.7 cm (H). RT, right; UP, upper pole; MP, mid pole; LP, lower pole; L, length; W, width; H, height.

She was prescribed etoricoxib and referred to endocrinology for subclinical hyperthyroidism. Thyroid function tests were repeated during follow-up. The free T4 remained in the normal range but TSH decreased from 0.16 to <0.0001 mIU/mL over a period of 2 months with a corresponding free triiodothyronine (T3) of 5.1 pmol/L (range of normality 3.5–6.0). Technetium-99m pertechnetate thyroid scintigraphy revealed overall reduced tracer uptake in the thyroid gland and a photopenic area in the right mid-to-lower pole which was suggestive of focal thyroiditis (Figure 2).

Figure 2 Technetium-99m pertechnetate thyroid scintigraphy showing overall reduced tracer uptake in the thyroid gland, and a photopenic area in the right mid-to-lower pole. TC, thyroid cartilage; SSN, suprasternal notch.

As she did not develop overt symptoms of hyperthyroidism, she was managed expectantly. Nine months later, her neck swelling resolved, TSH normalised and a repeat thyroid sonography showed resolution of all but one 0.5 cm nodule in the right lobe without suspicious features (Figure 3). The patient remained euthyroid and sonography showed no further change in the appearance of the nodule a year later (Figure 4).

Figure 3 Sonography of the thyroid gland 9 months after presentation. Grey-scale ultrasound images of the upper pole of the right thyroid lobe in longitudinal orientation (A) and mid to lower poles of the right thyroid lobe in longitudinal orientation (B). The nodule in the upper pole has shown interval reduction in size. The previously noted nodule in the mid to lower poles has resolved. RT, right; UP, upper pole; MP, mid pole; LP, lower pole; REG, region.

Figure 4 Timeline of clinic progress. TRAB, TSH receptor antibody; TSH, thyroid stimulating hormone; TPO, thyroid peroxidase; TG, thyroglobulin; NSAIDs, non-steroidal anti-inflammatory drugs.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Evaluation of a thyroid nodule is a common clinical scenario. As most patients with thyroid nodules are euthyroid, the focus of evaluation is to rule out malignancy. This usually requires sonographic assessment and FNAC of sonographically suspicious nodules. However, the clinical presentation and thyroid function should not be forgotten as the likelihood of malignancy in a thyroid nodule is lower in hyperthyroidism than in euthyroidism or hypothyroidism (2).

This patient’s history of a painful goitre hints at the differential diagnoses of thyroiditis. Thyroiditis can be practically classified as painful or painless. Painful thyroiditis consists of De Quervain’s, infectious, radiation-induced, or traumatic (such as palpation thyroiditis). Painless thyroiditis comprises Hashimoto thyroiditis, postpartum, medication-induced, or fibrosing (Riedel’s) thyroiditis. Each differential diagnosis will also present with a set of its own clinical features.

A differential diagnosis for the case presented is suppurative thyroiditis characterized by abscess formation in the thyroid gland. It is typically accompanied by fever, raised neutrophils, and a sonographically anechoic, ill-defined lesion within the thyroid gland. The lack of fever in our patient and the solid nature of her thyroid nodules make suppurative thyroiditis unlikely. Another differential diagnosis is toxic multinodular goitre given the subclinical hyperthyroidism. However, it is usually painless. Furthermore, the thyroid scintigraphy typically shows increased radiotracer uptake within the hyperactive nodules. Regression of benign nodule is possible as the sonographic features of the nodules in this patient are not highly suspicious of malignancy. However, in a prospective cohort of patients with cytologically benign, predominantly solid thyroid nodules, regression in size occurred in only 18.5% of the nodules over 5 years. Most of the benign nodules (70%) remained stable and complete disappearance of the nodules was rare (3). Finally, iodine deficiency can also cause goitres that regress with iodine repletion but this condition is accompanied by hypothyroidism and it may not necessarily be nodular (4).

De Quervain’s thyroiditis, also known as subacute or granulomatous thyroiditis, is the most likely diagnosis in this case. It is thought to be preceded by a viral infection (5). The resultant thyroid inflammation disrupts the follicles, resulting in a breakdown of TG, an uncontrolled release of T4 and T3, hence the development of a hyperthyroid state. Following the depletion of TG stores, the patient may enter a state of hypothyroidism as the inflamed thyroid gland is unable to synthesise new hormone, and TSH is concurrently inhibited. After the resolution of inflammation, synthesis of thyroid hormone gradually resumes, and the patient recovers to a euthyroid state although up to 15% may remain hypothyroid (6). De Quervain’s thyroiditis may also overlap with other existing thyroid conditions such as Grave’s disease (7).

Our patient’s brief period of painful goitre, the lack of antibodies against TG, TPO, TRAB and the photopenia on the thyroid uptake scan support the diagnosis of De Quervain’s thyroiditis. The spontaneous resolution of the hyperthyroidism also corroborated with its natural history. Inflammatory pseudonodules can be found in this condition and are known to resolve spontaneously.

Our patient is similar to another case report of a 39-year-old female who had presented initially with solitary thyroid nodule, subclinical hypothyroidism and an unremarkable FNAC. She then presented with neck pain and a Technetium-99m pertechnetate thyroid scintigraphy showed a reduced pertechnetate uptake. One difference was that she was given steroids following a trial of non-steroidal anti-inflammatory drugs (NSAIDs), with good effect. Similarly, her thyroid nodules resolved sonographically during subsequent follow-up (8).

The sonographic features of inflammatory pseudonodules are further described in the literature. In a study of 899 patients with nodules that had undergone FNAC if they are ≥5 mm in size, 28 patients were found to have pseudonodules (3.1%). The pseudonodules exhibited marked hypoechogenicity, smooth margin, ovoid shape, same vascularity as adjacent parenchyma, and no calcification. Most pseudonodules only show benign lymphocyte infiltration on FNAC. Except for the marked hypoechogenicity, the pseudonodules do not display other suspicious features (9).

The clinical course of our patient reveals that pseudonodules in De Quervain’s thyroiditis can be managed conservatively with NSAIDs and observation. A thorough history enquiring about pain and the symptoms of hyperthyroidism, a physical examination that elicits tenderness in a goitre, and thyroid function before sonography helped us to arrive at the diagnosis and avoided an invasive FNAC.

Conclusions

As thyroid nodules are increasingly diagnosed, it is timely to remember the entity of inflammatory pseudonodules that can spontaneously resolve. When faced with a hyperthyroid patient with thyroid nodules, consultation with an endocrinologist is recommended. This case illustrates the possibility of spontaneous resolution of thyroid nodules in patients with subclinical hyperthyroidism. Clinicians should recognize this to avoid performing unnecessary FNAC or generating excessive concerns about cancer in their patients.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://aot.amegroups.com/article/view/10.21037/aot-23-39/rc

Peer Review File: Available at https://aot.amegroups.com/article/view/10.21037/aot-23-39/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aot.amegroups.com/article/view/10.21037/aot-23-39/coif). H.L. serves as an unpaid editorial board member of Annals of Thyroid from September 2023 to August 2025. C.Y.Z.K. is a Medical Officer employed under the Ministry of Health Holdings, Singapore. The Ministry of Health Holdings is the holding company of Singapore’s public healthcare institutions that oversees the distribution of healthcare resources within Singapore which also includes determining the medical rotations for the doctors within the country through the Medical Officer Posting Exercise. However, it has not been involved in this case report. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. 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;14:587-95. [Crossref] [PubMed]
2. 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;26:1-133. [Crossref] [PubMed]
3. Durante C, Costante G, Lucisano G, et al. The natural history of benign thyroid nodules. JAMA 2015;313:926-35. [Crossref] [PubMed]
4. Nyenwe EA, Dagogo-Jack S. Iodine deficiency disorders in the iodine-replete environment. Am J Med Sci 2009;337:37-40. [Crossref] [PubMed]
5. Desailloud R, Hober D. Viruses and thyroiditis: an update. Virol J 2009;6:5. [Crossref] [PubMed]
6. Mariani G, Tonacchera M, Grosso M, et al. The Role of Nuclear Medicine in the Clinical Management of Benign Thyroid Disorders, Part 2: Nodular Goiter, Hypothyroidism, and Subacute Thyroiditis. J Nucl Med 2021;62:886-95. [Crossref] [PubMed]
7. Pichler R, Wölfl S, Bogner S, et al. Subakute Thyreoiditis mit Zellzerfall und passagerer Hyperthyreose in einer Basedow-Struma – Fallbericht. Acta Medica Austriaca 2002;29:137-40. [Crossref] [PubMed]
8. Bianda T, Schmid C. De Quervain's subacute thyroiditis presenting as a painless solitary thyroid nodule. Postgrad Med J 1998;74:602-3. [Crossref] [PubMed]
9. Jung SJ, Kim DW. Ultrasonographic and cytopathological features of an inflammatory pseudonodule in the thyroid gland. Diagn Cytopathol 2016;44:725-30. [Crossref] [PubMed]