Risk of malignancy
Male: 2 - 3 times increased risk.
Less than 20: Risk of malignancy doubled.
Above age 45: Increased risk of malignancy.
Above 70: Risk of malignancy quadrupled.
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 .
Low dose: 100 times increase risk of malignancy (lifetime risk).
High dose: 300 times increase risk of malignancy (lifetime risk).
Family history 
Presence of thyroid cancer in family members increases risk of malignancy.
The larger the tumour size, especially when >4 cm, or the presence of obstructive symptoms indicates higher risk of malignancy.
History of rapid growth in a few weeks indicates higher risk of malignancy.
Hoarse voice or vocal cord palsy with recurrent laryngeal nerve involvement 
Presence of hoarse voice or vocal cord palsy indicates high risk of malignancy.
Cervical lymphadenopathy 
Presence of cervical lymphadenopathy indicates high risk of malignancy.
Characteristics of thyroid swelling 
Firm/hard consistency or fixed swelling indicates high risk of malignancy.
Soft, mobile or cystic swelling indicates low risk of malignancy.