Embryological considerations of thyroid surgery: developmental anatomy of the thyroid, parathyroids and the recurrent laryngeal nerve.

The surgeon planning a thyroidectomy must be prepared to find variations in three important structures in the neck. He must be prepared to find ectopic thyroid nodules above, below or lateral to the normally located thyroid gland. Any unattached nodule should be considered malignant until proved otherwise. He must identify and preserve parathyroid glands that may not lie in the typical location. He must be prepared to encounter recurrent laryngeal nerves that do not recur. The surgeon who remembers the embryology of the structures in the neck may occasionally be astonished, but never surprised.