Solitary thyroid nodule

Risks for cancer
Solitary thyroid nodules are more common in females yet more worrisome in males. Other associations with neoplastic nodules are family history of thyroid cancer and prior radiation to the head and neck.

Radiation exposure to the head and neck may be for historic indications such as tonsillar and adenoid hypertrophy, "enlarged thymus", acne vulgaris, or current indications such as Hodgkin's lymphoma. Children living near the Chernobyl nuclear power plant during the catastrophe of 1986 have experienced a 60-fold increase in the incidence of thyroid cancer. Thyroid cancer arising in the background of radiation is often multifocal with a high incidence of lymph node metastasis and has a poor prognosis.

Signs and symptoms
Worrisome sign and symptoms include voice hoarseness, rapid increase in size, compressive symptoms (such as dyspnoea or dysphagia) and appearance of lymphadenopathy.

Investigations

 * TSH - A thyroid-stimulating hormone level should be obtained first. If it is suppressed, then the nodule is likely a hyperfunctioning (or "hot") nodule.  These are rarely malignant.
 * FNAC - fine needle aspiration cytology is the investigation of choice given a non-suppressed TSH. Repeat the FNAC in 6 months if the nodule enlarges.
 * Imaging - Ultrasound and radioiodine scanning.

Thyroid Scan
Cold - 85% of nodules are cold. Of these, up to 25% are malignant.

Hot - 5% of nodules are hot. Of these, 1% are malignant.

Surgery
Surgery should be performed in the following instances
 * Reaccumulation of the nodule despite 3-4 repeated FNACs
 * Size in excess of 4 cm
 * Complex cyst on thyroid ultrasound (showing solid and cystic components)
 * Compressive symptoms
 * Signs of malignancy (vocal cord dysfunction, lympadenopathy)