Cystic Lesions of the Thyroid
Thyroid cysts are common lesions that most often result from cystic degeneration in an adenomatous nodule. However, any type of thyroid nodule can undergo cystic degeneration, including follicular adenomas, follicular carcinomas, Hurthle cell neoplasms, and papillary thyroid carcinomas (PTCs). In some studies, as many as 15–25% of solitary thyroid nodules and up to 37% of all thyroid nodules are at least partially cystic. Often the cysts evolve secondary to hemorrhagic degeneration within the nodule. In addition to cystic degeneration of follicular-derived lesions, other nonfollicular cysts including thyroglossal duct cysts, branchial cleft-like cysts, and parathyroid cysts can also occur in or near the thyroid gland and are amenable to fine needle aspiration (FNA).