PALM BEACH, FLA. — Patients with Hashimoto's thyroiditis had a threefold increased risk of also having a well-differentiated thyroid cancer as compared with other patients undergoing thyroid resection, based on a review of 802 patients treated at one center.
The review also found no link between Hashimoto's thyroiditis (HT) and thyroid lymphoma. Both findings diverge from prior reports by other groups, which documented a high lymphoma incidence but no increased rate of papillary or follicular thyroid cancers, Dr. B. Mark Evers said at the annual meeting of the Southern Surgical Association.
“It makes sense that there is an association between the inflammation of Hashimoto's thyroiditis and well-differentiated cancers, as in the stomach and colon,” said Dr. Evers, professor of surgery at the University of Texas, Galveston. “I'm not sure why we saw more [of an association] than the published literature.”
“This is an important observation. It's discordant with most of the published literature,” said Dr. Robert Udelsman, professor and chairman of surgery at Yale University, New Haven, Conn.
Dr. Evers and his associates reviewed all patients who had a thyroid resection at his institution during 1987–2002. The 802 patients included 155 patients with a well-differentiated thyroid cancer only, 52 with HT only, 43 with both thyroid cancer and HT, and 552 who underwent a resection for another reason, often for laryngectomy. Papillary cancers were 88% of all thyroid cancers, and follicular were another 7%.
Thyroid cancer was about three times as common in patients with Hashimoto's thyroiditis as in those in the series without HT, “a strong link between inflammation and thyroid cancer,” said coinvestigator Dr. Shawn D. Larson, a surgeon at the University of Texas, Galveston.
Further analysis showed no association between HT or thyroid cancer and age, gender, race, or tumor size or aggressiveness.
Comparison of the demographic and clinical profile of the thyroid cancer patients treated in the Galveston study with that of more than 22,000 thyroid cancer patients in a National Cancer Institute database showed that the Galveston patients were typical.
Two proteins involved in cell growth and inflammatory responses were elevated to similar levels in patients with Hashimoto's thyroiditis and those with thyroid cancers, Dr. Evers said.