Cystic nodules can remain stable, occasionally get smaller and sometime continue to expand. Some cysts may rapidly expand due to bleeding or hemorrhage within the cyst. Rapidly expanding cysts can become symptomatic producing a noticeable lump in the neck, pain, difficulty swallowing and very rarely change in voice.
Cysts that are completely fluid filled have a much lower risk of thyroid cancer compared to cysts that have solid components. Diagnosis of a cystic thyroid lesion may be made at the time of ultrasound, or following a fine needle biopsy when fluid is obtained from the thyroid cyst. Spontaneous resolution of a thyroid cyst is rare but may occur in up to 15% of cases. Most large cysts or complex cysts should be aspirated with a fine needle to rule out the possibility of malignancy. Ultrasound-guided needle biopsies of a complex cystic nodule is necessary to insure that the biopsy material contains thyroid cells, and not just cystic fluid. Only these cells of the solid component will provide the necessary information whether the cystic nodule is of concern or not.
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For evaluation of a partly cystic nodule, the risk of cancer seems proportionate to the degree to which the nodule also contains solid components. Partially cystic nodules which contain at least 50% solid tissue, have a risk of malignancy that is similar to equal size nodules that are completely solid. On the other hand, largely cystic nodules with smaller solid components have a much lower risk of thyroid cancer, usually less than 5%.
Pure thyroid cysts may be managed in a variety of ways. Most commonly, pure thyroid cysts which are 3cm or less in size are merely observed and monitored for changes. Alternative management approaches for thyroid cysts are many including aspiration and instillation of ethanol or other ablative approaches. Simply aspirating thyroid cysts is largely ineffective with very rapid return of the cyst fluid. Thyroid surgery effectively removes thyroid cysts but is not commonly utilized unless there are multiple large thyroid cysts and they have become noticeable or symptomatic to the thyroid patient.