Endocrine Abstracts

A 24-year-old girl was referred with a massive thyroglossal duct cyst (TGDC) and an intra-cystic papillary thyroid cancer (PTC). The impressive clinical photographs, striking radiological images and histology slides are presented.

She presented eight and half months post partum with a 10 cm midline neck lump of 4 years duration. She was asymptomatic and was on levothyroxine for Hashimoto’s thyroiditis.

Clinically, there was a cystic mass extending from just above the level of the hyoid bone to the sternal notch. Ultrasound of the neck showed a long cystic structure lying to the right of the midline, deep to the strap muscles, likely to be a TGDC. Within the cyst there was a 1.5 cm solid papillomatous lesion, with features suspicious of PTC. There were no intrathyroidal lesions. The cervical lymph nodes were unremarkable. MRI of the neck revealed a complex multilobulated, partly septated cyst. Within the superior pole, an avidly enhancing lesion likely to represent a PTC was seen, corresponding to the ultrasound.

A fine needle aspiration would have required percutaneous drainage of the TGDC to improve cytological yield. Potentially this may have compromised complete surgical excision. Therefore, a Sistrunk procedure was performed, with the TGDC removed intact together with the body of the hyoid bone. Histology revealed a 9 cm long TGDC with an intra-cystic 1.2 cm PTC. No normal thyroid tissue was identified and excision was complete.

Due to the size of the PTC and the presence of Hashimotos’s thyroiditis, a total thyroidectomy was performed prior to receiving radioiodine ablation therapy.

The presence of PTC within TGDCs is recognised and occurs in approximately 1%. The management remains somewhat controversial with regards to thyroidectomy and radioiodine ablation. This TGDC was unusual due to its size and complexity, as well as the presence of Hashimoto’s thyroiditis.