A 45-year-old male presents with a long-standing, recurrently infected midline neck swelling diagnosed as a thyroglossal duct cyst. Biopsy of a suspicious nodule within the cyst reveals malignancy. What is the most common histological type of carcinoma found in a thyroglossal duct cyst?

Explanation

While rare, malignancy can arise within a thyroglossal duct cyst. The most common histological type of carcinoma found in a thyroglossal duct cyst is papillary thyroid carcinoma. This is because the thyroglossal duct is derived from thyroid tissue, and ectopic thyroid tissue can be present within the cyst, which can then undergo malignant transformation, most commonly into papillary carcinoma.