The University of Hong Kong's department of surgery has found a hereditary genetic link between a condition enlarging the thyroid gland and thyroid cancer. Although a possible link has been suggested before, this study is the first to find evidence proving it and could lead to better diagnoses. In a study published yesterday, medical researchers reported on following 304 thyroid cancer patients from Queen Mary Hospital between 1992 and 2007. Only 20 of these patients suffered from the thyroid gland enlargement condition known as goitre, before developing thyroid cancer. By running DNA tests, the team, led by Elly S.W. Ngan, found a hereditary gene mutation in two of the patients' families. Normally people inherit two healthy copies of a gene that supports the functions of the thyroid gland. However, in the two cases, the patients received one bad gene and one good one from their parents. Patients with the mutated gene all developed goitre and later more advanced thyroid cancer. 'We don't know why the other ... patients did not have this mutated gene,' assistant professor Merce Garcia-Barcelo said. 'The results of the study suggest that a significant proportion had a hereditary gene mutation.'