Malignant degeneration of thyroglossal duct cysts: Clinical aspects, imaging findings and management: Case series

Abstract

Introduction and importance

Thyroglossal duct cysts (TDCs) are congenital anomalies that can rarely undergo malignant transformation, with approximately 1 % of operated TDCs demonstrating malignant degeneration. Therapeutic management and follow-up methods are still controversial subjects.

Case series presentation

We report 3 cases of a papillary carcinoma of thyroid occurring in a thyroglossal duct cyst. The diagnosis was suspected preoperatively in 2 patients, hence the indication of frozen section examination. All patients underwent Sistrunk procedure associated with total thyroidectomy and central neck dissection. Concomitant papillary thyroid carcinoma was found in 2 patients. A complementary treatment by radioactive iodine 131 with frenetic hormone therapy was undertaken in all the cases. The follow-up showed no recurrence.

Clinical discussion

The clinical presentation of thyroglossal duct cyst carcinoma is often nonspecific, posing challenges in early diagnosis. The chosen treatment strategy, involving the Sistrunk procedure, total thyroidectomy, and central neck dissection, along with adjuvant therapy using radioactive iodine 131 and frenetic hormone therapy, was effective in preventing recurrence.

Conclusion

The management of degenerated TDC is based on a multidisciplinary approach. Papillary carcinomas of TDC generally have a good prognosis.

Highlights

• •TDCs are congenital anomalies that can rarely undergo malignant transformation in 1% of cases
• •The clinical presentation of TDC carcinoma is often nonspecific
• •Sistrunk procedure, total thyroidectomy, and central neck dissection, along with adjuvant therapy using radioactive iodine 131 and frenetic hormone therapy, are effective in preventing recurrence

1. Introduction

Thyroglossal duct cysts (TDCs) are congenital cervical malformations resulting from the incomplete resorption of the tract connecting the base of the tongue to the thyroid isthmus. While these cysts are generally benign, neoplastic degeneration is a rare occurrence, affecting approximately 1 to 1.5 % of cases [[1], [2], [3]]. The first documented instance of cancerization within the TDC dates back to the early twentieth century, credited to Brentano, and since then, approximately 250 cases have been reported in the medical literature [3,4].

Malignancy in thyroglossal duct cysts (TDCs) frequently exhibits latent presentation, with clinical manifestations closely resembling those of non-degenerated TDCs.

We aim to discuss three cases of TDCs with neoplastic transformation to identify clinical and para-clinical characteristics and explore therapeutic management modalities.

2. Methods

This case series includes three cases of degenerated TDC diagnosed and treated at the ENT department of Farhat Hached Hospital in Sousse that were evaluated between [2000−2022]. A retrospective analysis of their medical records was conducted, encompassing medical history, clinical information, and imaging data. The review included an assessment of management modalities, histopathological findings, and follow-up records.

The work has been reported in line with the PROCESS criteria [5].

3. Results

3.1. First case

This case report details a 76-year-old patient with a 20-year history of an upper anterior cervical mass, which had rapidly increased in size over the last 10 months, associated with dysphagia to solids. The clinical examination found a 5 cm elastic cervical mass adherent to the hyoid bone. Its surface was regular and it was sensitive to the palpation. No lymph nodes were noted. The Thyroid Lodge/bed was free. Cervical ultrasound showed a cystic cervical mass measuring 4 × 3 cm and a micro nodular goiter.

The CT scan revealed a para-median cervical formation of fluid density well encapsulated and gaining contrast in the periphery (Fig. 1). Thyroid function tests were normal. The patient had a Sistrunk procedure. The definitive histopathological examination concluded that a papillary thyroid carcinoma developed on a TDC. The patient then had a total thyroidectomy with left lymph node dissection 2 months later. Histological examination of the specimen showed 2 foci of thyroid micro-carcinoma (5 mm and 8 mm) associated with lymph node metastases. Additional treatment with radioactive iodine at a dose of 100mci was undertaken. No recurrence was observed during the 5-year follow-up period, as indicated by the white isotopic mapping on the whole-body scan and a negative thyroglobulin assay. The patient expressed contentment with the provided therapeutic approach.

Fig. 1.

Cervical CT in axial view before and after injection showing a cystic formation containing a parietal nodule which is enhanced after injection of contrast product.

3.2. Second case

A 65-year-old male presented to outpatient care for an upper anterior cervical swelling that had been evolving for 10 years, rapidly increasing in size since 6 months and no other functional signs. The examination objectified an 8 cm ad hyoid painless mass without satellite adenopathies. The thyroid bed was free.

Cervical ultrasound showed an upper vascularized cervical mass with both liquid and tissular components. A 1 cm hypoechoic nodule occupied the left lobe of the thyroid. Cervical CT scan revealed a voluminous cervical mass measuring 8x5cm with a honeycomb structure and enhancement of the tissular component after injection. The thyroid was the site of a 5 mm left mid-lobar calcified nodule (Fig. 2). The thyroid function studies were normal. The patient underwent a Sistrunk procedure with a midline cervical incision sacrificing a cutaneous paddle strongly adhering to the cervical swelling. Frozen section examination concluded that there was papillary carcinoma at the level of the cystic wall. The intervention was completed by a total thyroidectomy and bilateral central dissection. Frozen section examination revealed a focus of 0.3 cm calcified right mid-lobar papillary microcarcinoma and an oncocytic adenoma of the left lobe confirmed on definitive histopathological examination with no lymph node metastasis. The patient had isotopic totalization with frenetic hormone therapy. The evolution was good with a follow-up of 4 years.

Fig. 2.

Cervical CT in axial view before and after injection of contrast product showing a mass with both cystic and tissular components and significant enhancement of the tissue component after injection.

3.3. Third case

A 64-year-old patient, with a past history of hypertension, presented to our ENT department for a midline cervical swelling that had been evolving for 8 months, rapidly increasing in size and without any other associated signs. The clinical examination showed the presence of a 4 cm anterior cervical swelling under the hyoid bone, of firm consistency, painless, mobile on swallowing and on protrusion of the tongue. No cervical lymph nodes were noted. The thyroid lodge was free. Cervical ultrasound revealed a septated cystic lesion with finely echogenic contents measuring 4 cm, associated with two hyperechoic solid thyroid nodules of 11 and 12 mm. No associated lymphadenopathies were noted (Fig. 3). The patient underwent Sistrunk procedure with the frozen section showing the presence of a 0.5 cm papillary carcinoma located in the cystic wall. The intervention was completed by a total thyroidectomy with bilateral central dissection. The conclusive anatomopathological analysis (Fig. 4) determined the presence of an 8 mm focus of papillary micro-carcinoma in the left lobe of the thyroid, involving the capsule, and a second 2 mm focus, accompanied by lymph node metastasis. Subsequently, the patient underwent isotopic totalization followed by frenetic hormone therapy. Three years postoperative follow-up did not reveal any recurrence.

Fig. 3.

Neck ultrasound: Septated cystic neck mass with solid thyroid nodules in the left lobe of the thyroid.

Fig. 4.

The thyroglossal cyst is the site of an epithelial tumor proliferation with a papillary architectural pattern, primarily occupying the lumen (A: HE ×100, B: HE ×200). The tumor cells (C: HE ×400) exhibit nuclear abnormalities that are characteristic of papillary carcinoma, including clear nuclei (ground glass appearance) and occasionally grooved nuclei (“coffee-bean” appearance) that overlap.

4. Discussion

Neoplastic localizations in thyroglossal cysts are rare and affect 1 to 1.5 % of cysts [1,2]. These tumors occur mainly in adults around the fourth decade with a slight female predominance and are extremely rare in children [2,[6], [7], [8]]. In fact, less than 40 pediatric cases have been reported in the international literature. Clinical presentation, imaging and treatment remain similar to adults [1,2,6].

Numerous authors have investigated the genesis and origin of carcinoma within the thyroglossal duct cyst (TDC) to establish an appropriate therapeutic approach. It is crucial to differentiate between a thyroid-related carcinoma and a squamous cell carcinoma, as they appear to have distinct origins, leading to different management strategies.

4.1. For thyroid carcinomas

Given the absence of reported cases of medullary carcinoma within degenerated thyroglossal duct cysts (TDCs), some authors propose that the carcinoma originates de novo within the cyst. They suggest that the source could be ectopic thyroid islets present both in the cyst's wall and throughout the duct's path [1,9,10]. Others suggest that the thyroglossal duct provides a natural pathway for the spread of subclinical thyroid carcinoma and that cancerization provides a pathway for metastatic spread [2,11].

4.2. For squamous cell carcinomas, there are two theories

The first stipulates that squamous cell carcinoma on TDC develops from metaplasia of a focus of papillary carcinoma, hence the mixed forms described by certain authors [10,12]. The second considers that squamous cell carcinoma develops from metaplasia of the squamous or columnar epithelium within the TDC or tract [13,14].

Histologically, papillary carcinoma of the thyroid is the most prevalent, accounting for approximately 83 % of cases [1,9,11]. Other types include mixed carcinomas, Hürthle cell carcinomas, follicular carcinomas, adenocarcinomas, and squamous cell carcinomas [13,15,16]. Notably, there are no reported cases of medullary carcinoma in the literature. Medullary carcinoma originates from thyroid para-follicular C cells, which have a distinct embryological origin from thyroid cells.

Widstrom stipulates three histological criteria for maintaining the diagnosis of a primary carcinoma of thyroglossal duct cyst (TDC) [1,17]:

• •The carcinoma must be located at the level of the TDC wall.
• •It must be distinguishable from cystic lymph node metastases.
• •Verification of the absence of thyroid or another organ carcinoma is crucial.

Malignant transformation in thyroglossal duct cysts (TDCs) often remains latent, and the clinical presentation closely resembles that of a simple TDC, explaining its frequent incidental discovery during pathological examination of surgical specimens [1,2,4]. Nevertheless, certain clinical indicators should alert the clinician and raise suspicion of potential degeneration. These include the firm, immobile, and/or irregular nature of the cervical mass, rapid enlargement not associated with infectious episodes, and the presence of cervical lymphadenopathy [7,9,18].

Radiological signs that contribute to suspicion of neoplasia within the TDC include a solid character, the presence of calcifications and/or intra-cystic vegetations, and invasion of the cyst wall [17,19]. However, the only definitive preoperative confirmation of degeneration is provided by fine needle aspiration, which holds diagnostic significance [20].

Currently, while the surgical treatment of thyroglossal duct cysts (TDCs) is well-established, the management of malignant degeneration in TDCs remains a subject of controversy and is contingent upon the anatomopathological nature of the condition. The question arises regarding the necessity of augmenting the initial procedure with a total thyroidectomy. Some authors advocate for total cyst excision using the Sistrunk technique and argue against the need for a total thyroidectomy [9,11]. On the other hand, some teams recommend performing a total thyroidectomy as part of the initial surgical procedure [16,19]. Alternatively, some surgeons opt to perform both procedures in a single intervention if the preoperative diagnosis was established through fine needle aspiration or if an associated thyroid nodule is present [20].

Advocates for total thyroidectomy argue that this approach serves a dual purpose: eliminating the possibility of an associated thyroid carcinoma and ensuring better monitoring through thyroglobulin level measurements [1,2,19]. A meta-analysis by Patel et al. revealed that the extent of surgery for the thyroglossal cyst was a significant predictor of outcomes, with a 10-year overall survival rate of 75 % [16].

Plaza et al. as well as others [1,6,16], also require certain criteria to preserve the thyroid:

• ⁎Age under 45 years-old
• ⁎The absence of a history of cervical irradiation at a young age
• ⁎A tumor size less than 1.5 cm
• ⁎The absence of invasion of the cyst wall
• ⁎A low grade tumor
• ⁎R0 resection margin
• ⁎The absence of lymph node or distant metastases.

Thyroidectomy is typically reserved for patients who do not meet specific criteria. Authors supporting a limited intervention, such as the Sistrunk procedure, cite reasons such as the potential increase in morbidity associated with re-intervention, the low percentage of thyroid cancer found, the possibility of subsequent excision if cancer is discovered, and the generally favorable prognosis of thyroid cancer [9,21]. Immediate lymph node dissection is recommended when clinically or ultrasound-suspicious lymphadenopathy is present [1,3,9,11]. Following thyroidectomy, iodine-131 scintigraphy and thyroglobulin tests are performed. If tumor residues are identified on scintigraphy, ablative irradiation therapy is necessary. Additionally, suppressive-dose thyroid hormone therapy is consistently indicated [2,16].

For squamous cell carcinomas, treatment depends on the association with papillary carcinoma foci within the same degenerated thyroglossal duct cyst (TDC). Surgical excision, primarily through the Sistrunk procedure, is the standard treatment, adapted to locoregional extensions. This procedure suffices when the lesion is contained within the cyst. In cases of extra-parietal extension, a more extensive resection may be necessary, involving neighboring muscles, the thyroid, the tongue, or the larynx. Lymph node dissection is recommended only when palpable adenopathy is discovered. External radiotherapy is administered if excision is incomplete or in cases of local extension, recurrence, or lymph node metastases [13,14]. For mixed carcinomas containing both squamous cell and papillary carcinoma foci, the reported approach involves wide excision, total thyroidectomy, and irradiation therapy [12].

The prognosis of papillary carcinomas on TDC appears more favorable than that of thyroid carcinomas due to the rarity of distant metastases. The 5- and 10-year survival rates are estimated at 100 and 95.6 %, respectively, according to Patel [1]. Assessing the prognosis of squamous cell carcinomas is challenging due to the limited number of reported cases, but they tend to be more aggressive, with an estimated mortality of 36.3 % based on cases with proper follow-up [13,14]. Recurrences can occur several years or even decades later, underscoring the importance of lifelong surveillance [1,13].

5. Conclusion

As one of the most common congenital abnormalities in the neck, TDC are important to consider in the differential diagnosis of cervical masses. While malignant transformation of these cysts is rare, it can occur either through metastasis from distant carcinomas or the presence of clusters of thyroid cells. Benign cysts typically present as an anterior cervical mass without accompanying symptoms, but suspicions should arise in cases of rapid growth or the presence of a hard, fixed, and/or irregularly shaped mass.

The management of carcinoma arising from TDCs remains a subject of ongoing discussion. This context emphasizes the controversies surrounding the approach to malignant tumors in thyroglossal duct cysts. It is essential to recognize the potential diagnosis of synchronous carcinoma of the thyroid gland, as it significantly impacts the prognosis. Surgeons must carefully assess the extent of local and distant disease, conducting repeat cervical imaging if necessary to identify suspicious thyroid nodules and reevaluate the disease stage. This approach ensures better surgical control of the disease and facilitates additional therapies such as radioiodine and hormone ablation.

Consent

Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

Our institution does not require ethical approval for reporting individual cases (We maintained a high level of respect for both anonymity and confidentiality when presenting the patient in our case report.)

Funding

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Author contribution

Jihene Houas, Monia Ghammam: conceptualisation, and writing original draft-editing.

Eya Laabidi: data collection and writing the article.

Oussama Khalfi: study and interpretation of patient imaging examinations.

Mouna Bellakhdher: manuscript review and editing.

Mohamed Abdelkefi: supervision and validation.

The final version of the manuscript has been approved by all the authors.

Guarantor

Monia Ghammam.

Provenance and peer review

Not commissioned, externally peer reviewed.

Conflict of interest statement

None.