Thyroid cysts are a benign change in the thyroid, and are generally classified as first or second level in clinical analysis. Thyroid nodules may be solid or may have mixed echogenicity. The biggest difference between a thyroid nodule and a cyst is their composition: cysts usually contain fluid, whereas nodules may contain other substances. Secondly, the vast majority of cysts are benign, classified as sub-level. Nodules, however, may potentially be malignant, and are classified as third, fourth, or even fifth level. If it is a thyroid cyst, there is no need for excessive worry. If it is a thyroid nodule, it is crucial to complete an ultrasound classification and then schedule regular follow-up exams.