Hashimoto's Thyroiditis

The presence of varying degrees of lymphocytic infiltration around papillary thyroid carcinoma (PTC) in differentiated thyroid cancer (DTC) is a common finding. Pollock and Sprong regarded Hashimoto's thyroiditis as a premalignant lesion and recommended total thyroidectomy. In contrast, Crile and Hazard argued that there was no increased risk and considered lifelong thyroid hormone replacement therapy to be sufficient. Hirabayashi and Lindsay suggested that Hashimoto's thyroiditis is not a premalignant lesion and that patients with papillary thyroid carcinoma associated with chronic thyroiditis have a better prognosis. Harach and Williams investigated the changing incidence of thyroiditis and papillary thyroid carcinoma before and after iodine prophylaxis in an endemic goiter region of Argentina. Although they concluded that both conditions were related to the same underlying cause, they suggested that they were not directly associated with each other and even proposed that papillary thyroid carcinoma causes thyroiditis rather than thyroiditis causing papillary thyroid carcinoma. However, this issue has not yet been definitively resolved. In our own series, the rate of lymphocytic thyroiditis among patients with differentiated thyroid cancer was 14%. However, when only the cases treated after the mandatory iodine supplementation program began in 2000 were evaluated, this rate increased to 23%. This increase was undoubtedly influenced, at least in part, by the greater emphasis placed on this finding during pathological examinations.

In clinical practice, the surgical treatment of a nodule developing within or enlarging in the setting of Hashimoto's thyroiditis is currently an accepted approach. Studies suggest that patients with differentiated thyroid cancer accompanied by chronic thyroiditis may have a somewhat better prognosis than those without chronic thyroiditis.