Abstract #1388241: A Rare Case of an Intrathyroidal Bronchogenic Cyst

Abstract

Bronchogenic cysts are uncommon congenital cystic malformations that arise due to dysplasia during ventral foregut development of the respiratory tract. They are mostly asymptomatic but can grow in size, causing compressive symptoms secondary to infection or malignancy. Bronchogenic cysts are usually located in the mediastinum or intrapulmonary regions, although they can rarely present in ectopic extrathoracic locations such as the thyroid. Here we report a rare case of an intrathyroidal bronchogenic cyst. A 48-year-old woman was incidentally found to have a thyroid mass on magnetic resonance imaging (MRI) neck by her neurologist during workup for migraines. An initial thyroid ultrasound showed a 4.7 cm left thyroid cyst with no concerning features, and a repeat follow up ultrasound 6 months later reported no change in its size. TSH, free T3, and free T4 were unremarkable. However, the patient began to endorse fullness in her neck that progressed to compressive symptoms, including dysphagia with solids and liquids, shortness of breath, and mild dysphonia. Endocrinology and otolaryngology (ENT) were consulted. ENT performed a nasopharyngolaryngoscopy, which was unremarkable for masses. A fine-needle aspiration (FNA) drained 25 mL of cystic fluid with non-diagnostic pathology with a virtually acellular specimen. FNA for parathyroid hormone level was low at 6 pg/mL (10 to 55 pg/mL), not suggesting parathyroid tissue. Compressive symptoms initially improved after FNA, but within 1 month her symptoms returned. Repeat thyroid ultrasound after FNA showed a 2.6 x 2.0 x 3.8 cm cystic nodule with regular margins. The patient opted for thyroid lobectomy as opposed to repeat aspirations. Her thyroid lobectomy was uncomplicated. The surgical biopsy was consistent with an intrathyroidal bronchogenic cyst. Her symptoms resolved after surgery and at her 3-month follow appointment, she continued to do well with resolution of symptoms. Bronchogenic cysts are quite rare in the thyroid. To our knowledge, there have only been 6 cases of intrathyroidal bronchogenic cysts previously reported. Bronchogenic cysts can grow in size causing compressive symptoms, with simple aspiration having a high rate of recurrence. Infection or, less commonly, transformation into malignant tumors are possible complications. Treatment for asymptomatic bronchogenic cysts remains controversial. However, once symptomatic, surgical resection is recommended over observation. Prognosis is generally excellent without recurrence for full resections.