The incidence of malignancy among patients with Graves' disease who were residents of one Minnesota county was examined in 342 patients between 1935 and 1967. During 4,736 person-years of observation, 32 malignancies were diagnosed; 24 cases were expected and the difference is not significant. Four cases of breast carcinoma were found vs five expected. Other tumor sites were cervix (five), uterus (two), rectosigmoid colon (three), stomach (two), larynx (two), and lung (two). There were three cases of leukemia, and in nine other sites one cancer each was recorded. There was a slightly higher than expected incidence of malignancy in patients who had received131I therapy; this finding requires further study in a larger patient population. Among patients who received thyroid hormone, the observed incidence of breast cancer was not significantly different from the expected incidence in our population.
(Arch Intern Med 138:944-947, 1978)