Table 1 Risk factors for thyroid malignancy. Baseline UK annual incidence for thyroid cancer: 2 - 3/100,000 population [3].

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.