Parental cancer and risk of papillary and follicular thyroid carcinoma.

In a population-based case-control study in the Uppsala-Orebro Health Care Region of Sweden, the histories of cancer among parents of 517 histologically confirmed cases of papillary and follicular carcinoma and of a similar number of sex- and age-matched controls were compared. The parental history of cancer was compiled through information from death certificates and from the nationwide Cancer Register. The incidence of malignancies in a cohort of parents of cases of thyroid cancer was also compared with the incidence in the whole Swedish population. A maternal history of cancer was more common among women with follicular carcinoma than among their controls (OR 2.11, 95% CI 0.96-4.67). Parents of probands with papillary carcinoma had an increased risk of thyroid cancer (OR 4.25, 95% CI 1.16-10.89), and mothers of probands with follicular carcinoma had an increased risk of stomach cancer (OR 3.65, 95% CI 0.99-9.35) compared with the general population. Cancer of the lung, breast, and pancreas were less common than in the general population. Familial cases of thyroid cancer were not limited to the papillary type. An inheritable pattern of carcinogenesis is possible for certain differentiated non-medullary thyroid cancers, but shared environmental exposures may also explain the parent-child associations of cancer in this study.