Thyroid Cysts
Thyroid cysts are nodules containing fluid — either entirely (simple cysts) or mixed with solid tissue. Most are benign and many resolve or remain stable.
The main concern is that cystic or mixed nodules can harbour cancer in the solid component, so ultrasound assessment matters.
Last medically reviewed: 1 November 2025
Types and significance
Simple cysts — entirely fluid-filled — are almost always benign. Complex cysts with solid components or septations need closer evaluation because the solid portion could contain malignancy.
Cysts may bleed internally, causing sudden pain or rapid enlargement — usually self-limiting but worth checking.
Evaluation
Ultrasound distinguishes simple from complex cysts and assesses any solid components. Purely cystic nodules rarely need FNAC; complex cysts with solid portions follow standard nodule evaluation criteria.
TSH testing excludes a functioning component.
Management
Simple cysts need no treatment — periodic ultrasound confirms stability. Recurrent or symptomatic cysts may be aspirated (drained with a needle), though recurrence is common. Surgery is reserved for cysts that recur repeatedly, cause compressive symptoms, or have suspicious solid components.
Frequently asked questions
Do thyroid cysts need to be removed?
Most do not. Simple cysts are monitored; only recurrent, symptomatic or suspicious cysts are considered for aspiration or surgery.
Can a cyst be cancer?
A purely fluid-filled cyst is almost never cancerous. Complex cysts with solid components require evaluation of the solid part — which is where cancer, if present, would be found.
Why did my cyst suddenly hurt?
Cysts can bleed internally, causing rapid painful enlargement. This usually settles, but should be checked with ultrasound to confirm nothing else is going on.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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