Thyroidectomy as a pathogenic factor in the evolution of thyroid cancer

In a group fo 860 patients with thyroid cancers (TC), 66 were found having had thyroid surgery for benign disorder more than 5 years before the diagnosis of TC. More than 70% of these patients were operated upon 10 or more years ago. The incidence of cancers developing in thyroid postsurgical remnants could thus be estimated to 5.5-7.7% of all thyroid cancers. These patients had predominantly follicular cancers and usually were older than 40 years at the age of diagnosis of TC. Unusually high incidence of distant metastases (pulmonary or osseous) was proved compared to other patients with TC, while the increase of patients having both pulmonary and osseous metastases was not found. It seems that the risk of developing TC late after thyroid surgery is somehow connected with endemic goitre areas, as all such reports arise from the central European area. Whichever the pathogenic mechanism may be, all patients following surgery for benign eumetabolic goitres should be checked up in regular intervals with regard to the possible benign or malignant recurrence. Patients operated upon because of hyperthyroidism do not seem to carry any similar risk.