Ultrasound-guided percutaneous microwave ablation treatment for toxic multinodular goiter: a case report

Introduction

Hyperthyroidism is a common disease with a global prevalence of 0.2–1.3% (1). Toxic multinodular goiter (TMNG), also known as Plummer’s disease, is a prevalent cause of thyrotoxicosis secondary to Graves’ disease (2). It consists of one or more autonomous thyroid nodules, or of one or more autonomous nodules combined with one or more non autonomous solid, cystic, or mixed (solid and cystic) nodules, or many small autonomous regions associated with a range of thyroid function disorders from subclinical hyperthyroidism to severe hyperthyroidism (3). It accounts for approximately 10% of all cases of hyperthyroidism (1).

There are two effective and relatively safe definitive treatment options for TMNG: radioactive iodine (RAI) treatment and thyroid surgery (4). Both methods have their own advantages and disadvantages, and treatment plans should be selected based on specific clinical conditions. According to the 2016 American Thyroid Association Guidelines, alternative therapies such as ethanol or radiofrequency ablation (RFA) can be considered for treating TMNG in certain patients who are unable to undergo RAI, surgery, or long-term antithyroid drug (ATD) treatment due to medical reasons or personal preference (4). TMNG is mostly treated with radioiodine (¹³¹I) or thyroidectomy but is rarely treated with microwave ablation (MWA). Here, we present a case of a young female with TMNG who underwent ultrasound-guided percutaneous MWA to control hyperthyroidism and reduce the size of her thyroid nodules. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-63/rc).

Case presentation

In December 2023, a 33-year-old Chinese female was admitted to Suzhou Hospital affiliated Medical School of Nanjing University who complained of thyroid nodules for 3 years.

In 2020, this patient went to the local hospital for a physical examination. She was diagnosed with thyroid nodules, but the report was not provided. In January 2021, she visited the Shanghai Ruijin Hospital for her thyroid nodules. Thyroid ultrasound showed several thyroid nodules by calcification in the both thyroid lobes with diffuse lesion. Some thyroid nodules were classified as TI-RADS 4A. She was diagnosed with hyperthyroidism based on the increase of Free Triiodothyronine (FT3), free thyroxine (FT4), and the decreased levels of thyroid-stimulating hormone (TSH), but the thyroid globulin antibody (TGAb), thyroid peroxidase antibody (TPOAb) and thyrotropin receptor antibody (TRAb) were negative. She was not treated with any anti-hyperthyroidism drugs. Ultrasound guided percutaneous fine-needle aspiration biopsy (FNAB) of thyroid nodules was performed, and the histopathology showed benign nodular goitre. Due to being in the outpatient clinic, she did not receive a thyroid scan. However, her follow-ups with a doctor were irregular.

The patient visited our outpatient department for the reexamination in December 2023. She exhibited occasional palpitations, discomfort, and a slight weight loss. The thyroid ultrasound was performed using a EPIQ7 scanner (Philips Ultrasound, Inc., Shanghai, China) with a 6–15 MHz probe. The ultrasound revealed multiple, solid, hypoechoic or mixed echogenicity masses in both thyroid lobes, ranging in size from 1.3 cm × 0.5 cm to 3.2 cm × 1.9 cm. Color Doppler flow imaging (CDFI) displayed blood flow signals around and within the nodules. Several lymph nodes signals were detected in the bilateral neck zone, with a size ranging from 0.7 cm ×0.5 cm to 1.5 cm ×0.7 cm (Figure 1). Thyroid function examination revealed hyperthyroidism with an FT4 level of 26.30 pmol/L (normal range, 11.48–22.70 pmol/L), an FT3 level of 11.22 pmol/L (normal range 3.54–6.47 pmol/L), and a TSH level of 0.003 mIU/L (normal range, 0.55–4.78 mIU/L) (Table 1). She was negative for TGAb, TPOAb and TRAb.

Figure 1 Preoperative ultrasound examination of the thyroid. 2D, two-dimensional; CF, color flow; Dyn R, dynamic range; P Med, penetration/medical imaging; Res, resolution; WF, wall filter.

Relevant examinations were completed after admission. In a state of complete rest, her vital signs were monitored, revealing a temperature of 36.6 ℃, a heart rate of 64 beats per minute, a respiration rate of 18 breaths per minute, and a blood pressure of 124/82 mmHg. Single-photon emission computed tomography combined with computed tomography (SPECT/CT) (GE NM Discovery^TM, General Electric, Wisconsin, USA) showed multiple nodules with high uptake (hot) in the both lobes, suggesting TMNG. Fifteen minutes after intravenous injection of 99mTcO4, an enlarged right lobe of the thyroid and a reduced left lobe were observed. The morphology of both lobes appeared irregular, with multiple regions of abnormal radioactive uptake. The surrounding thyroid tissue showed low uptake and unclear imaging (Figure 2). The RAI uptake rate (RAIU) of thyroid was not increased, 24.62% (normal range, 14.15–29.35%) in 3 hours and 28.4% (normal range, 22.09–42.91%) in 24 hours. After the patient’s routine blood test and coagulation time test showed normal results, she underwent ultrasound-guided FNAB of thyroid nodules in the both lobes successfully with two needle aspirations again. She underwent a repeated thyroid nodule biopsy in order to rule out hyperthyroidism caused by thyroid adenocarcinoma. The pathological diagnoses were benign nodules in the both lobes (Figure 3).

Figure 2 SPECT/CT examination of the thyroid before the first MWA. MWA, microwave ablation; SPECT/CT, single-photon emission computed tomography combined with computed tomography.

Figure 3 Pathological reports from FNAB. FNAB of nodules in the left (A) and right (B) lobes of the thyroid gland. Hematoxylin and eosin staining; magnification: 100×. FNAB, fine-needle aspiration biopsy.

After obtaining the patient’s consent, we proceeded with an ultrasound-guided percutaneous MWA to reduce the size of the nodules. Compared to RFA, MWA offers faster heating speed, higher temperatures, and stronger penetration, making it more suitable for larger thyroid nodules and shorter ablation times. This procedure was performed under local anesthesia. The effect generated by microwaves would lead to protein denaturation and dehydration of glandular cells. Coagulation necrosis would be experienced in the thyroid gland after ablation, ultimately resulting in a reduction of its volume. The main thyroid ablation procedures were as follows: we performed preoperative conventional ultrasound to measure the size of the thyroid nodules and plan the puncturing route of the microwave antenna. Local anesthesia was achieved using 0.5% lidocaine, administered from the skin to the thyroid capsule under real-time ultrasound guidance. Additionally, 15 mL of physiological saline with 5 mL of 0.5% lidocaine mixture was injected as an isolation fluid to separate the thyroid from the anterior cervical muscle group, thereby minimizing damage to surrounding structures. The microwave antenna was inserted into the thyroid, and MWA was performed targeting the thyroid nodules. This was continued until the presence of hyperechoic gas, indicative of gasification reaction, was observed. The total MWA duration was 8 minutes and 52 seconds. Immediately following the ablation, CDFI was performed, revealing no discernible blood flow signals within the ablated zones. The patient’s postoperative condition was stable. There were no postoperative complications such as bleeding, fever, hoarseness, cough, difficulty breathing, or thyrotoxic storm.

In January 2024, the patient was readmitted to Suzhou Hospital affiliated Medical School of Nanjing University for MWA treatment. During this admission, the patient’s thyroid function was reexamined and it was found that their levels of FT3 and FT4 were significantly lower than before. Thyroid function examination showed that FT4 level was 15.91 pmol/L (normal range, 11.48–22.70 pmol/L), FT3 level was 5.61 pmol/L (normal range, 3.54–6.47 pmol/L), and TSH level was 0.011 mIU/L (normal range, 0.55–4.78 mIU/L) (Table 1). Additionally, the tests for TGAb, TPOAb, and TRAb all were negative. The SPECT/CT of thyroid showed the nodules have shrunk after MWA compared to their previous size (Figure 4). After the patient’s routine blood test and coagulation time test results came back normal, she underwent an ultrasound-guided percutaneous MWA of thyroid nodules in the both lobes successfully again. The total MWA duration was 7 minutes and 18 seconds. She suffered from low thermal and neck pain after the operation, but these symptoms subsided the next day.

Figure 4 SPECT/CT examination of the thyroid before the second MWA. MWA, microwave ablation; SPECT/CT, single-photon emission computed tomography combined with computed tomography.

Fourteen weeks after the second MWA, the patient returned to Suzhou Hospital affiliated Medical School of Nanjing University for a follow-up visit. The thyroid function test results were within the normal range (Table 1). The thyroid ultrasound showed a 54% decrease in the volume of ablated nodules in the left lobe and a 56% decrease in the volume of ablated nodules in the right lobe.

All procedures performed in this case were in accordance with the ethical standards of the institutional research committee and in line with the Helsinki Declaration and its subsequent amendments. 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

Hyperthyroidism is a condition in which the thyroid gland becomes overactive, leading to an excessive production and release of thyroid hormones into the blood circulation. It affects approximately 2% of women and 0.2% of men (5). The main causes of hyperthyroidism include Graves’ disease, TMNG, thyrotoxic adenoma, human chorionic gonadotrophin (hCG) related hyperthyroidism, iodine-induced hyperthyroidism, pituitary hyperthyroidism. Thyroid hormone has a significant impact on nearly every tissue and organ system. Untreated or partially treated thyrotoxicosis can lead to various health complications, including weight loss, tremors, atrial fibrillation, muscle weakness, embolic events, osteoporosis and neuropsychiatric symptoms (4). In rare cases, it can even result in cardiovascular collapse and death (6,7). Therefore, effective control of hyperthyroidism is crucial.

Thyroid nodules are a common occurrence in the general population, especially in cases of iodine deficiency (8). This deficiency can have a chronic stimulating effect on the thyroid, leading to the development of diffuse or nodular goitre and, eventually, thyroidal autonomy (9). Genetic factors, being female, and smoking are all contributing factors to the development of nodules (10). Functional autonomy occurs in approximately 5% of thyroid nodules, either as solitary toxic adenomas or as part of a multinodular goiter. Although TMNG is the second reason of hyperthyroidism, it is still considered an uncommon condition.

Currently, it is believed that RAI therapy or thyroidectomy is recommended for patients with overtly TMNG (4). On occasion, long-term, low-dose treatment with methimazole (MMI) may be appropriate (11). For patients with TMNG, the risk of treatment failure or need for repeat treatment is less than 1% after undergoing near-total or total thyroidectomy, in contrast to a 20% risk of requiring retreatment after RAI therapy (12-14). Euthyroidism is typically achieved within a few days after surgery. However, after undergoing a near-total or total thyroidectomy, there is a 100% chance of developing hypothyroidism and requiring treatment with exogenous thyroid hormones. Patients with TMNG who undergo RAI treatment typically experience a 50–60% response rate within 3 months, which increases to 80% within half a year (12,14,15). A comprehensive study of patients with TMNG who received RAI therapy revealed that the incidence of hypothyroidism was 3% after 1 year and 64% after 24 years (16). Both RAI therapy and thyroidectomy carry a high risk for developing hypothyroidism. Therefore, percutaneous ultrasound-guided ethanol injection and radiofrequency are newer alternative options for managing TMNG (4,17), which can be considered in some patients with RAI, surgery and long-term ATD that are unsuitable, contraindicated or rejected. The patient in our case is more inclined to opt for a minimally invasive method.

However, the two treatments, percutaneous ethanol injection and radiofrequency, each have their own pros and cons. A standard procedure for percutaneous ethanol injection involves the injection of ethanol into the autonomous area of a TMNG. One study found that the average patient required four sessions at 2-week intervals (18). About 93% of patients achieved a functional cure, as evidenced by no uptake on RAI scintigraphy, and 92% of patients experienced a reduction in nodule size of more than 50% (18). In a separate another study examining both TA and TMNG, it was found that 78% of cases achieved a functional cure, with all nodules regressing and no instances of recurrent hyperthyroidism during a 5-year follow-up period (19). However, the use of ethanol has been restricted due to the pain caused by its leakage into surrounding tissues, as well as other negative effects. These have included temporary hyperthyroidism, permanent facial numbness on the same side as the injection, fibrosis around the injection site that can complicate future surgeries, and toxic damage to the larynx and nearby skin (20,21). Another minimally invasive treatment for TMNG is RFA. A meta-analysis had shown that RFA leads to greater reductions in nodule size with fewer treatment sessions compared to laser therapy (22). RFA had been shown to reduce nodule volume by 82%; however, it should be noted that 18% of patients may still experience hyperthyroidism following the treatment (23). All patients reported experiencing pain during the procedure; however, there were no complications. Advocates of RFA believed that compared to surgery or RAI, it could preserve normal thyroid function (24), which was its advantage.

Because of concern about postoperative hypothyroidism and a surgical scar on her neck, the patient we reported refused RAI and surgery. She chose MWA as her treatment method due to its minimally invasive nature and guidance by ultrasound images. This thermal ablation technique can accurately destroy lesions under real-time imaging guidance without damaging surrounding tissues, nerves, and blood vessels (11). MWA is known for its ability to generate high levels of heat, penetrate deeply, and quickly ablate tissue, resulting in shorter operation times. These advantages make it particularly suitable for larger or deeper nodules, as well as those with a rich blood supply, ultimately leading to a lower rate of postoperative recurrence. Compared to RFA, MWA offers several advantages, including higher power and temperature, as well as minimal impact from the heat sink effect (25). In recent years, MWA has become increasingly utilized for the ablation of malignant tumors and volume reduction of hypertrophic organs (26). To our knowledge, MWA has not been widely used in the treatment of TMNG so far. In this type of procedure, the primary complications may include local bleeding, nerve injury and vascular damage. It is important to carefully monitor for these potential risks and take necessary precautions to prevent them. The conventional approach to preventing these complications is through intraoperative fluid isolation.

After carefully comparing the effectiveness, cost-efficiency, and invasiveness of MWA and RFA, we have chosen MWA as the preferred treatment. Conducting a preoperative assessment of the patient’s metabolic level, utilizing real-time ultrasound guidance during the procedure, and implementing proper fluid isolation techniques are crucial for ensuring the success, safety, and effectiveness of this treatment. The patient’s thyroid function gradually returned to normal after 14 weeks following the second ablation. The volume of ablated thyroid nodules was significantly reduced. However, the specific long-term effect of MWA treatment for TMNG still needs to be observed. Furthermore, additional research and exploration is necessary to determine the ablation time, specific output power, and ablation volume required for postoperative thyroid function changes, improvement of hyperthyroidism, and prevention of hypothyroidism. This information is crucial for our understanding and treatment of these conditions.

Conclusions

In conclusion, ultrasound-guided percutaneous MWA is an effective, safe and minimally invasive method for treating TMNG. It is a viable alternative to the two traditional treatment methods.

Acknowledgments

We thank the patient for her cooperation in this study and all the clinicians for their contribution.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-63/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-63/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-63/coif). The 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 case were in accordance with the ethical standards of the institutional research committee and in line with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for the publication of the case report. 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/.

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