Ultrasound-guided minimally invasive treatment of nonfunctional parathyroid cysts: a description of five cases

Introduction

Parathyroid cysts (PCs) account for 0.08–3.41% of parathyroid diseases (1). The etiology of PCs may involve residual third or fourth parotid fissures from embryonic development, aggregates of peripheral small cysts, and the fusion of parathyroid follicles, although the exact pathogenesis remains unclear (2). PCs are categorized as functional parathyroid cysts (FPCs) and nonfunctional parathyroid cysts (NFPCs) based on the presence of hyperparathyroidism (3,4). FPCs can release large amounts of parathyroid hormone (PTH) into blood, leading to symptoms of hyperparathyroidism and hypercalcemia. In contrast, NFPCs only produce high levels of PTH in the fluid within the cyst. At present, the diagnosis of PC can be made through ultrasound (US), cytological analysis, and measurement of PTH levels in the cystic fluid (5). Most FPCs may require surgical treatment, while as for NFPCs, intervention is required when compression symptoms are severe. Fine-needle aspiration (FNA) and cyst sclerotherapy have been widely accepted for achieving cosmetic improvements in cyst treatment in recent years. If the patient cannot tolerate sclerotherapy, relief of compression symptoms can be achieved through FNA alone, although this method is susceptible to recurrence. Cyst aspiration sclerotherapy can emerge during the development of US-guided interventional procedures. Various sclerosing agents have been used in clinical practice, such as polidocanol, dehydrated alcohol, and glacial acetic acid. In considering the patient’s condition, sclerotherapy may be selected after FNA to effectively treat PCs and minimize the risk of recurrence.

Case presentation

We conducted a review of 5 cases treated in the Ultrasound Intervention Department of Zhejiang Hospital between January 2023 and January 2024. The data and relevant clinical parameters of these patients are summarized in Table 1. 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 each patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Case 1

The patient, a 32-year-old woman, attended hospital for dysphagia and suspected thyroid issues. The palpated mass was smooth and soft with no contact or pressure pain. A computed tomography (CT) scan showed a well-defined round low-density mass in the posterior-inferior part of the left thyroid gland (Figure 1A,1B). A US scan revealed an oval echogenic cystic mass in the lower left lobe of the thyroid gland measuring approximately 5.28 cm × 3.65 cm × 3.25 cm with well-defined margins (Figure 1C). The mass compressed the trachea with a slight deviation to the right. The parathyroid-related serum markers were within normal limits. FNA extracted 30 mL of aqueous cystic fluid with a PTH level of 1,284 pg/mL, leading to a diagnosis of NFPC. The cyst was then treated with polysilanol injection sclerotherapy, which provided symptomatic relief. Subsequent follow-up examination 6 months later indicated no recurrence of the cyst (Figure 1D).

Figure 1 US and CT images of parathyroid cyst (Case 1). (A) CT showed a cystic low-density shadow in the left lobe of the thyroid gland that was 39.24 mm × 35.18 mm in size. (B) CT coronal view of the neck showing the location and adjacency of the cyst. (C) The longitudinal image of ultrasonography of the left lobe of the thyroid gland showed a cystic nodule with regular morphology that was 5.28 cm × 3.25 cm in size. (D) US image review 6 months after cyst-sclerosing surgery. US, ultrasound; CT, computed tomography.

Case 2

The patient, a 37-year-old woman, presented with a painless mass palpable in her neck. US revealed a 7.29 cm × 4.91 cm × 4.09 cm cystic mass attached to the left lobe of her thyroid gland (Figure 2A). A contrast-enhanced computed tomography (CECT) scan showed a round, liquid density mass in the left thyroid gland, causing the trachea to be slightly shifted to the right, without enhancement (Figure 2B). The patient’s serum calcium, PTH, and thyroid function tests were all normal. Due to the patient’s strong aesthetic concerns, we performed sclerotherapy with polycinnamon sclerotherapy after FNA aspiration of 28 mL of clear cystic fluid. The PTH level of the cystic fluid was found to be 1,681 pg/mL, and cytopathology revealed no abnormal cellular components. US of the neck 6 months later showed no significant abnormalities at the original lesion site (Figure 2C).

Figure 2 US and CT images of parathyroid cyst (Case 2). (A) US showed a cystic mass in the lower pole of the left lobe of the thyroid gland that was 7.29 cm × 4.09 cm in size. (B) CECT showed a liquid density shadow in the left lobe of the thyroid gland with no enhancement, which had shifted the trachea to the right. (C) US showed no recurrence on review 6 months after cystic sclerotherapy. US, ultrasound; CT, computed tomography; CECT, contrast-enhanced computed tomography.

Case 3

The patient, a 75-year-old woman, attended the Zhejiang Hospital with neck discomfort. A CECT scan showed a cystic low-density shadow of about 45.34 mm × 32.22 mm × 25.78 mm in the thyroid, without enhancement (Figure 3A,3B). The US revealed a large cystic nodule measuring about 4.87 cm × 3.32 cm × 1.43 cm just below the lower pole of the right thyroid gland, protruding into the upper mediastinum near the aortic arch (Figure 3C). Associated serologic tests were normal. The patient, who had a history of primary hypertension, coronary atherosclerosis, and type 2 diabetes mellitus, declined surgery and underwent FNA of the cyst. Twenty-one milliliters of clear watery fluid was withdrawn, showing a PTH level of 1,873 pg/mL with a few lymphocytes, suggesting a diagnosis of NFPC. Due to the cyst’s proximity to the aortic arch, the option of sclerotherapy was not pursued to avoid potential complications. The sclerotherapy could have led to the fibrosis of the peripheral tissues (e.g., blood vessels) caused by sclerosing agent leakage or chemically damaged adhesions. As a result, the patient’s neck compression symptoms were greatly relieved after FNA. We agreed with the patient and recommended that she be followed up for observation. After 6 months, a follow-up US scan showed that the remaining cyst was approximately 2.29 cm × 1.22 cm × 1.08 cm in size, and the patient’s serum PTH and calcium levels were normal, with only mild neck discomfort (Figure 3D).

Figure 3 US and CT images of parathyroid cyst (Case 3). (A) CT showed a cystic low-density shadow 32.22 mm × 25.78 mm in size in the right lobe of the thyroid gland with a maximum cross-sectional area, protruding downward into the thorax. (B) CECT showed a cystic neck mass with no enhancement and clear well-defined margins. (C) The longitudinal image of ultrasonography of the right lobe of the thyroid gland showed a cystic nodule 4.87 cm × 1.43 cm in size with irregular morphology. (D) US review of the neck 1 month after FNA revealed a recurrent cyst 2.29 cm × 1.08 cm in size close to the aortic arch. US, ultrasound; CT, computed tomography; CECT, contrast-enhanced computed tomography; FNA, fine-needle aspiration.

Case 4

The patient, a 52-year-old woman, presented with an occasional choking cough. US showed a cystic mass beneath the left thyroid lobe measuring about 5.24 cm × 4.40 cm × 3.07 cm in size (Figure 4A). A CT scan showed a cystic low-density area in the left thyroid lobe, measuring approximately 46 mm in length (Figure 4B). Laboratory results indicated normal levels of serum calcium, PTH, and thyroid function. Approximately 23 mL of fluid was drained from the cyst via FNA, and the PTH level was 1,587 pg/mL (Figure 4C). Symptoms were relieved after intervention, and after 6 months, her choking cough improved but was accompanied by a slight pressure sensation in her neck. Subsequent US indicated a recurrence of a cystic mass measuring approximately 4.03 cm × 3.76 cm × 2.04 cm below the left thyroid lobe.

Figure 4 US, CT, and cyst fluid after FNA of a parathyroid cyst (Case 4). (A) US showed a cystic mass located just below the left thyroid lobe that was 4.40 cm × 3.07 cm in size. (B) CT showed a cystic low-density shadow in the left thyroid lobe. (C) FNA extracted approximately 23 mL of fluid from the cyst. US, ultrasound; CT, computed tomography; FNA, fine-needle aspiration.

Case 5

A 47-year-old woman had a neck mass detected during a physical examination and a right deviation of the trachea on chest X-ray, without any other symptoms. US showed a cystic mass immediately below the left thyroid lobe measuring approximately 5.67 cm × 4.64 cm × 3.97 cm. A CT scan showed a lesion in the left lower pole of the thyroid gland, measuring about 56.21 mm × 47.56 mm × 34.84 mm in size, with clear borders and a homogeneous low-density shadow. Serum calcium and PTH levels were normal. The PTH value of the cyst fluid obtained by FNA was 1,534 pg/mL. Cytology showed a small cellular specimen with no signs of malignant cytology. Symptoms were relieved after the intervention, and the cyst had grown to two-thirds that of its original size after 6 months, with no obvious clinical symptoms.

Discussion

PCs is a rare type of cystic mass found in the neck, accounting for less than 1% of cases. It is most commonly seen in middle-aged and older adult women. PCs are typically solitary, often located near the lower pole of the thyroid gland (6-8), and may be mistaken for thyroid cysts. The development of PCs may be associated with mechanisms such as congenital disorders and microcystic aggregates (3,9). NFPCs, which accounts for about 80% of PCs cases, typically presents as an asymptomatic neck mass (10,11). However, larger cysts can cause compression symptoms such as dyspnea, dysphagia, and hoarseness (6,12,13).

US is effective in distinguishing between cystic and solid lesions and in assessing their proximity when diagnosing neck masses (14). As it pertains to cystic nodules located in the lower pole of the thyroid gland, US findings can potentially indicate PCs (8). However, it can be challenging to differentiate between PCs, thyroid cyst, thyroglossal cyst, and other adjacent structures (2). Abboud et al. (15) reported that US has a high accuracy rate (90%) in visualizing parathyroid lesions that are 8–60 mm in diameter. Additionally, the expertise of sonographers is crucial in differentiating between PCs and thyroid cysts (16).

PCs can be difficult to differentiate from inferior thyroid pole cysts. After reviewing and analyzing US images of the patients in this series, we formulated the following points to help with differentiation: (I) it is recommended that the patient be instructed to make a swallowing movement during the examination. PCs moves out of sync with the ipsilateral thyroid gland during a swallowing maneuver. In contrast, thyroid cysts move in sync with the thyroid gland during swallowing. (II) The position of the cysts in relation to the inferior thyroid artery should be noted, as PCs are generally located on the lateral side of the inferior thyroid artery, while thyroid cysts are more often located on its medial side. (III) Thyroid cysts typically exhibit greater intracapsular tension, while PCs tend to have less. PCs are usually irregularly shaped, softer in texture, and have a larger aspect ratio (Figure 5A,5B).

Figure 5 Example diagram of PCs and thyroid cysts. (A) PCs have a low tension, soft texture, and are often irregular in shape. (B) Thyroid cysts tend to be firmer, more tense, and distinctly separate from the thyroid gland. PC, parathyroid cyst.

Imaging can only provide qualitative information about the cystic solidity of the mass, while FNA is essential for diagnosing PCs (17). When the aspirated cyst fluid is tested for PTH levels that exceed the levels found in the blood at the same time, it can be used to diagnose PCs (18). In 1953, Crile et al. (11) reported the first case of PCs diagnosed by FNA. In contrast, FNA is not recommended for FPCs, which should be treated with surgical excision (10). Therefore, conducting serum PTH and calcium tests before FNA is necessary to differentiate between FPCs and NFPCs. US-guided FNA with the simultaneous analysis of cyst fluid thyroid hormone and PTH levels may help determine further management of cysts in cases of NFPCs.

For NFPCs, intervention is necessary if it causes compressive symptoms. According to the literature, surgical treatment is recommended to prevent recurrence. Percutaneous cystic FNA therapy can be used for both diagnosing and treating NFPCs (19). The indications of FNA for NFPCs include (I) physical condition that cannot tolerate the procedure, (II) pregnant women, (III) patient refusal of the procedure, (IV) aesthetic requirements favoring minimal invasiveness, and (V) an inability to tolerate cystosclerosis. Before aspiration treatment, the optimal puncture point should be evaluated and selected. After local infiltration of anesthesia, the cystic cavity is punctured with an 18-G puncture needle under US guidance. With the needle tip located in the cystic cavity, the needle core is extracted, the syringe is connected with the extension tube to pump the fluid, and full pressure is applied after the fluid is completely pumped. Close attention should be paid to changes in the patient’s vital signs.

In the treatment of cystosclerosis in the 2 cases discussed in this paper, polidocanol (polyoxyethylene lauryl ether) was used as the sclerosing agent after cyst aspiration. Polidocanol destroys the secretory function of the endothelial cells of the capsule wall, causing the capsule lumen to adhere and eventually disappear. The indications for cystic polidocanol sclerotherapy are (I) US suggestive of benign cystic nodules or predominantly cystic mixed cystic-solid nodules with a diameter of ≥2 cm, (II) pathologic puncture biopsy confirmed benign nodules, and (III) presence of compressive symptoms or cosmetic concerns. Absolute contraindications for this procedure include (I) allergy to the sclerosing agent, (II) severe cardiopulmonary insufficiency, (III) coagulation disorders, and (IV) recent use of cephalosporins. The relative contraindications are lactation, pregnancy, and menstruation in women (20). The cases were treated as follows: the size and location of the cyst had been determined, and informed consent was obtained from the patient before the procedure was initiated. In this procedure, the patient is positioned in the supine position with full exposure of the neck. After routine disinfection, toweling, and local infiltration anesthesia, FNA is performed, followed by the injection of a mixture of SonoVue suspension and saline into the cystic cavity, which can indicate whether the contrast enhancement is confined to the intracystic cavity and whether the cystic wall is intact. Following repeated rinsing with saline and the injection of 10 mL of polidocanol, the solution is left in place for 3 minutes and then withdrawn. Sterile dressings are used to cover the puncture points, and pressure bandages are applied. The patients are closely observed postprocedure.

For the cases in this report, CECT of the neck was performed before both simple cyst aspiration and cyst aspiration sclerotherapy. This helped in clarifying the location of the cyst for needle localization. After analyzing the aspirated cystic fluid, we diagnosed the cases as NFPCs. None of the patients experienced hematoma, allergy, pain, nausea, or fever after the intervention. Their compression symptoms were relieved, and there were no significant abnormalities in the serum PTH. At the 6-month postintervention review, patients who had received sclerotherapy showed no recurrence, while the other patients experienced recurring cysts without significant compression symptoms.

Acknowledgments

We would like to thank the five patients and their families for providing consent to use their data in these case descriptions.

Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-1921/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 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 each patient for publication of this article 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. Halenka M, Frysak Z, Koranda P, Kucerova L. Cystic parathyroid adenoma within a multinodular goiter: a rare cause of primary hyperparathyroidism. J Clin Ultrasound 2008;36:243-6. [Crossref] [PubMed]
2. Wei Y, Liu Y, Yang L, Xu H, Yang Y, Liang Y, Zhang Y, Yang A, Tang X, Xue J. 99mTc-methoxyisobutylisonitrile single-photon emission computed tomography/computed tomography parathyroid imaging in the diagnosis of functional parathyroid cysts: an initial experience. Gland Surg 2024;13:32-44. [Crossref] [PubMed]
3. Luan T, Guido M, Whittington E, Jantsch D, Kurtin AD. Parathyroid Cyst and Micropapillary Thyroid Carcinoma: A Case Study of Unexpected Concurrent Endocrine Pathologies. Cureus 2024;16:e67208. [Crossref] [PubMed]
4. Wirowski D, Wicke C, Böhner H, Lammers BJ, Pohl P, Schwarz K, Goretzki PE. Presentation of 6 cases with parathyroid cysts and discussion of the literature. Exp Clin Endocrinol Diabetes 2008;116:501-6. [Crossref] [PubMed]
5. Armstrong J, Leteurtre E, Proye C. Intraparathyroid cyst: a tumour of branchial origin and a possible pitfall for targeted parathyroid surgery. ANZ J Surg 2003;73:1048-51. [Crossref] [PubMed]
6. Ahmad MM, Almohaya M, Almalki MH, Aljohani N. Intrathyroidal Parathyroid Cyst: An Unusual Neck Mass. Clin Med Insights Endocrinol Diabetes 2017;10:1179551417698135. [Crossref] [PubMed]
7. Papavramidis TS, Chorti A, Pliakos I, Panidis S, Michalopoulos A. Parathyroid cysts: A review of 359 patients reported in the international literature. Medicine (Baltimore) 2018;97:e11399. [Crossref] [PubMed]
8. Xu P, Xia X, Li M, Guo M, Yang Z. Parathyroid cysts: experience of a rare phenomenon at a single institution. BMC Surg 2018;18:9. [Crossref] [PubMed]
9. Rossi ED, Revelli L, Giustozzi E, Straccia P, Stigliano E, Lombardi CP, Pontecorvi A, Fadda G. Large non-functioning parathyroid cysts: our institutional experience of a rare entity and a possible pitfall in thyroid cytology. Cytopathology 2015;26:114-21. [Crossref] [PubMed]
10. Rajasekaran S, Barwad A, Mitra S. Non-functioning parathyroid cyst presenting as a neck mass. Autops Case Rep 2024;14:e2024505. [Crossref] [PubMed]
11. Crile G Jr, Perryman RG. Parathyroid cysts; report of five cases. Surgery 1953;34:151-4.
12. El-Housseini Y, Hübner M, Boubaker A, Bruegger J, Matter M, Bonny O. Unusual presentations of functional parathyroid cysts: a case series and review of the literature. J Med Case Rep 2017;11:333. [Crossref] [PubMed]
13. Zhang XU, Yuan JH, Feng LU, Shan DQ, Wu JF, Liu ST. Giant non-functional parathyroid cyst: A case report. Oncol Lett 2016;11:2237-40. [Crossref] [PubMed]
14. Collins B, Stoner JA, Digoy GP. Benefits of ultrasound vs. computed tomography in the diagnosis of pediatric lateral neck abscesses. Int J Pediatr Otorhinolaryngol 2014;78:423-6. [Crossref] [PubMed]
15. Abboud B, Sleilaty G, Rabaa L, Daher R, Abou Zeid H, Jabbour H, Hachem K, Smayra T. Ultrasonography: highly accuracy technique for preoperative localization of parathyroid adenoma. Laryngoscope 2008;118:1574-8. [Crossref] [PubMed]
16. Ujiki MB, Nayar R, Sturgeon C, Angelos P. Parathyroid cyst: often mistaken for a thyroid cyst. World J Surg 2007;31:60-4. [Crossref] [PubMed]
17. Fadda G, Rossi ED. Liquid-based cytology in fine-needle aspiration biopsies of the thyroid gland. Acta Cytol 2011;55:389-400. [Crossref] [PubMed]
18. Go P, Watson J, Lu Z, Carlin A, Hammoud Z. Robotic resection of a mediastinal parathyroid cyst. Gen Thorac Cardiovasc Surg 2017;65:52-5. [Crossref] [PubMed]
19. Naqvi SHA, Hung P, Allen D, Naqvi SHS, Ricks ET, Saluja K, Eguia AA, Karni RJ. Infected Ruptured Parathyroid Cyst Presenting with Hypercalcemia and Airway Obstruction: A Case Report. Ear Nose Throat J 2023; Epub ahead of print. [Crossref]
20. Dong YJ, Liu ZH, Zhou JQ, Zhan WW. Efficacy of Lauromacrogol Injection for Ablation of Benign Predominantly Cystic Thyroid Nodules and Related Factors: A Prospective Study. Korean J Radiol 2022;23:479-87. [Crossref] [PubMed]