Carcinoma of dual ectopic thyroid gland in a patient with cyanotic congenital heart disease--a case report and review of literature.

Carcinoma arising from an ectopic thyroid gland in the absence of a normal thyroid gland is uncommon. There is a clinically relevant and unique association of ectopic thyroid with congenital heart disease which in turn is related to thyroid embryogenesis. The median thyroid anlage develops adjacent to the newly differentiated myocardium during the 3rd week of intrauterine life. The downward pull exerted by continued descent of heart is postulated to assist in the descent of the thyroid to its final location in the lower cervical position. Ectopic thyroid tissue can result from abnormal heart development or abnormal interaction between thyroid primordium and heart. We present a rare association of cancer of the ectopic thyroid gland in a patient with congenital heart disease.