Table 1.

Risk factors for thyroid malignancy. Baseline UK annual incidence for thyroid cancer: 2 - 3/100,000 population [3].

Risk factors	Risk of malignancy
Gender [4,9]	Male: 2 - 3 times increased risk.
Age [4,8]	Less than 20: Risk of malignancy doubled. Above age 45: Increased risk of malignancy. Above 70: Risk of malignancy quadrupled.
Ionising radiation [3,10]	Latency period is usually 10 - 15 years and mostly occurs 20 - 30 years after exposure.
	There is a 40% absolute risk of malignancy for a thyroid nodule in a patient with previous radiation exposure [9].
	Low dose: 100 times increase risk of malignancy (lifetime risk).
	High dose: 300 times increase risk of malignancy (lifetime risk).
Family history [3]	Presence of thyroid cancer in family members increases risk of malignancy.
Tumour size [4,11]	The larger the tumour size, especially when >4 cm, or the presence of obstructive symptoms indicates higher risk of malignancy.
Rate of growth [3,10,11]	History of rapid growth in a few weeks indicates higher risk of malignancy.
Hoarse voice or vocal cord palsy with recurrent laryngeal nerve involvement [11]	Presence of hoarse voice or vocal cord palsy indicates high risk of malignancy.
Cervical lymphadenopathy [11]	Presence of cervical lymphadenopathy indicates high risk of malignancy.
Characteristics of thyroid swelling [11]	Firm/hard consistency or fixed swelling indicates high risk of malignancy. Soft, mobile or cystic swelling indicates low risk of malignancy.