Case study - Thyroglossal cyst

The possible causes for this neck swelling were explored, by Dr Keith Barnard

A neck swelling that caused concern
A neck swelling that caused concern

Mr Jackson was 52 and someone I didn't see very often. He told me his wife had sent him because she had noticed a swelling in his neck. He thought it had probably been there for about six months and was very slowly getting bigger. He used to smoke, but had not done so for more than 20 years. Nevertheless, his wife was convinced he had cancer.

On questioning, he said he had no pain, no night sweats and no difficulty in swallowing or breathing. It had not affected his voice.

'It wasn't bothering me at all,' he said, 'and that's why I didn't want to bother you.'

There was nothing of note in his personal or family history, he was not taking any medication and he drank little alcohol.

Key points
  • Thyroglossal cyst occurs equally in males and females.
  • More common in younger patients, but may present at any age.
  • A midline structure that moves upwards on swallowing and on tongue protrusion.
  • Surgery is the treatment of choice.
  • Malignancy is rare (about 1%).

A general examination showed all to be normal, apart from the swelling in the front of his neck.

At first glance, it seemed like a very prominent Adam's apple, but it was smooth and soft, measuring about 3cm x 4cm, and I convinced myself it was probably fluctuant, although it was difficult to be certain because pressing on the swelling made him feel uncomfortable.

It was in the midline and when he swallowed or put out his tongue, it seemed to move upwards slightly. There were no other discrete swellings or lymphadenopathy.

I was fairly sure it was not malignant and explained that it was probably a thyroglossal cyst.

Mr Jackson was relieved and wanted to leave and tell his wife. I explained this was my provisional diagnosis and we needed to make sure. I thought I should do routine bloods and TFTs, and when he came back a week later, I was able to tell him the results were normal. I then arranged for him to have an ultrasound of his neck.

Ultrasound of the neck

The ultrasound showed a midline cystic mass anterior to the thyroid, consistent with a thyroglossal cyst.

I explained that these cysts have their origins in the development of the embryo, when the thyroid descends down the thyroglossal duct to take up its position in the neck. This duct is normally reabsorbed, but if a remnant remains, the lining can secrete a mucus-like substance and cause a swelling. Although they are more common in younger people, they can present at almost any age, even into the nineties.

Mr Jackson agreed to be referred for surgical removal of the cyst. I explained this was advisable to confirm the diagnosis and exclude malignancy. If the cyst remained, there was a risk of infection. If it grew larger, it would be a problem cosmetically. Thyroglossal cysts can also become cancerous, although this is rare.

Mr Jackson underwent Sistrunk's procedure, which involves resecting the track of the duct, the cyst and the mid-section of the hyoid. He was very pleased with the result. The basic elements of this operation have stood the test of time, as it was first described as long ago as 1920.1

Differential diagnoses

The list of differential diagnoses is long, but the main ones to consider include enlarged lymph nodes, lipoma and sebaceous cyst, cystic hygroma, carotid aneurysm, submandibular gland enlargement, a pharyngeal pouch and benign or malignant thyroid swellings, especially in the isthmus or from ectopic thyroid tissue.

The cysts can occur anywhere along the track of the thyroglossal duct, from within the tongue, above or below the hyoid, or in the larynx, although this is very rare.

About 7% of the population is thought to have thyroglossal duct remnants, which are found equally in males and females.

The almost pathognomonic sign of a thyroglossal cyst, where it moves upwards with swallowing or when the patient protrudes their tongue, is because the thyroglossal duct is also attached to the hyoid bone and the peritracheal fascia.

  • Dr Barnard is a former GP from Fareham, Hampshire

Reference

1. Sistrunk WE. The surgical treatment of cysts of the thyroglossal tract. Arch Surg 1920; 71: 121-2

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