A Middle-aged Woman With Recurrent Intrathyroidal Parathyroid Cyst Treated With Ethanol Sclerotherapy

Abstract

Background/Objective

Parathyroid cysts (PC) are a rare cause of cervical masses, with an ectopic intrathyroidal location being even more rare, with only 9 cases reported in the literature. We present a case of a recurrent intrathyroidal cyst successfully treated with ethanol sclerotherapy.

Case Report

A 64-year-old woman presented to our clinic in 2017 with a cervical prominence and recurrent pressure sensation in her left lower neck. She had a history of multiple cyst aspiration drainage procedures for a recurrent intrathyroidal PC. Ultrasound revealed a simple cyst measuring 5.1 cm × 2.1 cm × 1.7 cm encompassing most of the left thyroid lobe. Parathyroid hormone level in the cyst fluid was elevated, but serum calcium and parathyroid hormone levels were within normal range. To prevent additional recurrences, ethanol sclerosis of the cyst was performed. After 6 years of follow-up, the patient remains asymptomatic and without evidence of PC recurrence.

Discussion

Although surgical resection of PC can be performed, in the case of an intrathyroidal PC, this would involve loss of functional thyroid tissue and the potential risk of postoperative hypothyroidism. Ethanol sclerosis has been successfully utilized to shrink both thyroid cysts and orthotopically positioned PCs while preserving thyroid tissue. In this case, ethanol sclerosis was used to successfully manage an intrathyroidal PC.

Conclusion

Based on the excellent response in this case and reports of efficacy of sclerosis in orthotopically positioned PCs, we conclude that ethanol sclerotherapy seems to be an effective treatment option for recurrent intrathyroidal PCs.

Highlights

• •Parathyroid cysts (PCs) are an extremely rare cause of cervical masses.
• •Ectopic cervical presentation of PC has been barely described in the literature.
• •PCs may or may not be functional, with functional cysts tending to occur in men and at more advanced ages.
• •Recurrent intrathyroidal PC treated succesfully with ethanol sclerotherapy.

Clinical Relevance

Given the rarity of the intrathyroidal presentation of a parathyroid cyst, this case joins the 9 other cases already reported in the literature to date, generating more interest about this pathology. The case presented demonstrates successful ethanol sclerosis of a large 5-cm intrathyroidal parathyroid cyst with excellent response in cyst shrinkage and preservation of thyroid and calcium levels within the normal range as well as lack of cyst recurrence.

Introduction

With an incidence between 0.075% and 5.0%, parathyroid cysts (PCs) are a rare cause of cervical masses, with a frequent probability of being misdiagnosed.1, 2, 3, 4, 5, 6 Crile reported the first case of PC diagnosed by fine needle aspiration in 1953.¹ So far, about 359 cases have been reported in the world literature.^4,7 They usually present as an asymptomatic neck mass or are incidentally detected during radiological imaging for unrelated indications. Percutaneous injection of sclerosants into the cyst has been documented as an effective treatment for recurrent cysts in the thyroid gland several times since 1979, which raised the possibility of treating PCs in the same manner.8, 9, 10 Sclerotherapy treatment for nonfunctional PC has been described since 1986, with sclerosant agents such as ethanol, tetracycline, showing the efficacy of this approach.^6,8 Ethanol sclerotherapy has been used as a nonsurgical option for recurrence of nonfunctional PCs since 1996 according to the literature.⁹ Our objective is to present the case of a middle-aged female with recurrent reaccumulation of fluid within an intrathyroidal PC over a 25-year period with successful durable resolution of the cyst after sclerotherapy with ethanol.

Case Report

A 64-year-old woman presented to our clinic in 2017 with a cervical prominence and recurrent pressure sensation in her left lower neck. Her medical history was positive for a herniated cervical disc and a benign thyroid nodule for which she had been taking levothyroxine 50 mcg daily. In addition, 24 years previously, an initial diagnosis of intrathyroidal PC was made at an outside hospital, with a record of multiples aspiration drainages being performed over the years. Aspiration yielded a clear acellular fluid each time. The concentration of parathyroid hormone (PTH) in the cyst fluid was found to be 372 pg/mL in 2008. Serum calcium levels ranged between 9.2 and 9.4 mg/dL (normal range, 8.9-10.1 mg/dL), and serum PTH levels remained between 23.8 and 34 pg/mL (normal range, 15-65 pg/mL). There was no history of any attempt to either remove the cyst surgically or treat it with sclerosis therapy. The physician examination at the presentation in 2017 was notable for the presence of a neck mass in the lower left neck, and laboratory testing was unremarkable, including thyroid-stimulating hormone (TSH), free thyroxine (T4), and serum calcium. A neck ultrasound revealed a 5.1-cm × 2.1-cm × 1.7-cm simple cyst that encompassed most of the left thyroid lobe (Fig. 1). To achieve long-term symptomatic relief, the patient was offered percutaneous ethanol sclerotherapy, and she agreed to the procedure. Under local anesthesia, 7 mL of clear fluid was drained from the cyst with an 18-gauge needle (Fig. 2), followed by intracystic administration of 9 mL of 95% absolute ethanol. After a 5-minute dwell time, 4 to 5 mL of the cyst fluid was aspirated to decompress the cyst and relieve pressure (Fig. 2). The sclerotherapy was well tolerated, only causing a transient moderate pressure sensation and resulting in 100 pg/mL of PTH in the cyst fluid.

Fig. 1.

Ultrasound revealed a simple cyst encompassing most of the left thyroid lobe measuring 5.1 cm × 2.1 cm × 1.7 cm.

Fig. 2.

(1) First, 7 mL of clear fluid was drained from the cyst; second, 9 mL of ethanol was injected; and third, (2) 10 mL of orange fluid was removed to decompress the cyst and relieve pressure.

Five months later, the patient’s neck remained asymptomatic, and a sonographic examination confirmed almost complete resolution of the cyst, with just a minute (2-3 mm) of residual hypoechogenicity being evident (Fig. 3). Laboratory testing remains unremarkable with a serum calcium level of 9.3 mg/dL, a serum PTH level of 33 pg/mL, a TSH level of 0.7 mIU/L, and a free T4 level of 1.3 ng/dL. Thyroid ultrasound imaging 3 and 6 years after ethanol sclerotherapy revealed no evidence of cyst recurrence, and serum PTH, calcium, TSH, and free T4 levels were all within the reference range. At the most recent follow-up, the patient remained asymptomatic, still on stable levothyroxine replacement therapy (dose of 50 mcg daily), and with laboratory results showing a calcium level of 9.3 mg/dL (8.9-10.1), a TSH level of 1.0 mIU/L (0.3-4.2), and a free T4 level of 1.3 ng/dL (0.9-1.7).

Fig. 3.

Resolution of the left intrathyroidal cyst after ethanol sclerosis after 5 months.

Discussion

The usual location for PCs is orthotopic, meaning that they are found in the typical anatomic position for parathyroid glands. However, parathyroid gland placement can vary in individuals, and the term ectopic is used when the parathyroid gland or PC is found outside the region of normal parathyroid placement, including intrathyroidal parathyroid adenomas or PCs. Parathyroid cysts are a rare cause of cervical masses, with an ectopically positioned intrathyroidal location being even rarer, with only 9 cases reported in the literature.10, 11, 12 A review of the literature revealed 1 case report of a documented intrathyroidal parathyroid adenoma being treated with sclerosis therapy, but a literature search did not identify any case reports of ethanol sclerosis for an intrathyroidal PC.¹³

PCs are classified as either functional or nonfunctional depending on their ability to produce and secrete PTH.^14,15 Available data indicate that most PCs are nonfunctional, are found more commonly in females, and typically occur in the inferior parathyroid glands. Functional PCs are more frequently diagnosed in males and at more advanced ages.¹ A difficulty in distinguishing intrathyroidal PCs from thyroid cysts has been encountered. Thyroid cysts tend to yield more opaque fluid with a brownish coloration, while the presence of clear aqueous fluid is more highly suggestive of a PC, with high PTH levels within the fluid being indicative of the diagnosis of PC.^1,15 In both functional and nonfunctional PCs, fluid or needle wash-out assessment yields a PTH concentration that is greater than that found in the serum. While thyroid lobectomy is an option for the management of intrathyroidal PCs, surgery tends to be reserved for functional cysts associated with hypercalcemia causing primary hyperparathyroidism.^5,16 Repeat aspiration drainage can be performed for PCs, but there tends to be a high recurrence rate. Other more permanent treatment options include surgical excision or sclerotherapy with agents such as tetracycline or ethanol, with the latter being preferred for the treatment of nonfunctional thyroid cysts more recently.^12,16

Regarding this case report, we present a patient with a large, recurrent intrathyroidal PC with mild cervical pressure symptoms and lack of biochemical evidence of hyperparathyroidism, with the PTH levels from the cyst fluid measuring 100 pg/mL and 372 pg/mL on 2 separate occasions. PTH levels ≥100 pg/mL are typically accepted as the cutoff for confirming the presence of PTH-secreting tissue. Our patient was initially managed with serial aspiration, but durable resolution of the cyst was achieved by means of sclerosis therapy with ethanol.

A literature review revealed reports on 19 patients with orthotopically located nonfunctional PCs from 1996 to 2023 who underwent successful ethanol sclerotherapy with minimal complications, such as mild discomfort from the needle, transient hoarseness, and dysphonia. The risks associated with the procedure should always be reviewed beforehand with the patient.17, 18, 19 A systematic review and meta-analysis published in 2017 yielded 218 relevant articles from 1905 to 2016 with 359 documented cases of PCs. They found that 61.6% of the PCs were nonfunctional and were twofold more likely to occur in females. Management consisted of surgical excision in 80.8%, aspiration drainage in 15%, and sclerotherapy in 4.2%.⁴ A retrospective study from 2013 evaluated the outcomes of simple aspiration in comparison to ethanol ablation for the treatment of nonfunctional PC. The group consisted of 12 patients who presented with a visualized or palpable neck mass, dysphagia, or neck discomfort. Cyst fluid PTH levels ranged between 95.1 and 5000 ng/dL. Simple aspiration was performed as the first choice of treatment in all 12 patients. The cyst recurred in 66.66% (8 patients) after 1 to 6 months of follow-up; all 8 patients in this group underwent ethanol sclerotherapy, with 6 having successful cyst shrinkage with 1 treatment and 2 patients undergoing a second session of ethanol sclerosis. The results revealed a statistically significant reduction in volume, dropping from a baseline of 23 ± 18.9 mL down to 0.04 ± 0.07 mL (P = .012); improvement in cosmetic appearance (P = .011); and reduction in compression-type symptoms (P = .01). These results support ethanol sclerosis as an effective nonsurgical option for the management of orthotopically positioned nonfunctional PCs.¹⁵

Our case report demonstrates successful ethanol sclerosis of a large 5-cm recurrent intrathyroidal PC with excellent response in cyst shrinkage and preservation of normal thyroid function and calcium levels as well as lack of cyst recurrence. The effect was durable as there has been a lack of cyst recurrence over 6 years of observation, and the patient feels well and continues to be on a stable dose of levothyroxine (50 mcg/d) as prior to the procedure.

Based on the excellent response in this case and reports of sclerosis efficacy in orthotopically positioned PCs, we conclude that ethanol sclerotherapy seems to be an effective treatment option for recurrent intrathyroidal PCs.

Disclosure

The authors have no multiplicity of interest to disclose.