Does Follicular Carcinoma of Thyroid from Endemic Region Behave more Aggressively?

Full text: Over a period of 10 years (1992-2002), a total of 196 patients of differentiated thyroid carcinoma (DTC) were treated in our department with high dose radioiodine based on a standard protocol. A thorough analysis of the patient records revealed that there were 11 (5.6%) cases of follicular thyroid carcinoma who presented initially with distant metastases without any suspicion of thyroid gland abnormality. DTC presenting with distant metastases at the time of initial diagnosis is rare. There is no large series but a few case reports have been publishes. In our patients, all the 11 were found to come from Sub-Himalayan endemic goiter region and all of them had the histopathological diagnosis of follicular carcinoma. At the time of presentation, 4 had metastases to vertebral column, 2 to skull and spine, 1 to skull, vertebra and both lungs, 1 had involvement of both humerus and femur and 1 each showed metastases in mandible, skull and sternum only. Clinical examination of thyroid gland of these patients revealed no abnormality in 8 cases, 2 had small solitary nodules (<1.5 cm.) and 1 enlargement of the gland without nodularity. All patients were subjected to near total thyroidectomy followed by repeated high dose radioiodine therapy and hormone substitution during the interval. Apart from 2 patients who died with in 6 months of the diagnosis, other 9 patients showed various degrees of improvement and were alive during the follow up period of 2-6 years. Out of the total patients (n=196), 56 (28.5%) were having follicular carcinoma. The incidence of distant metastases was found to be 46% in 26 cases. This is much higher than that reported in the literature. On the basis of the fact that 46% of follicular thyroid carcinoma patients coming from a known endemic goiter region had distant metastases and all the 11 patients of occult thyroid carcinoma with distant metastases were histopathologically proven follicular carcinoma, it appears that follicular carcinoma in endemic goiter regions behaves more aggressively than in non-endemic areas. Hence a more aggressive therapy and frequent follow-up are necessary in such patients. (author)