High prevalence of breast cancer in patients with benign thyroid diseases

In patients with breast cancer (BC) a high prevalence of benign thyroid diseases (BTD) has been described, Hashimoto's thyroiditis accounting to a large extent for this association. The aim of this study was to evaluate the prevalence of BC in a large group of patients with BTD.

Clinical records of 622 consecutive patients with BTD were examined. BC prevalence in BTD patients was compared with BC frequency in general population living in the same country.

BC prevalence in patients with BTD (38/622; 6.11%) was significantly higher (p=0.0002) compared to BC frequency in general population (2.07%). When patients were divided according to the age of menopause, in females older than 49 yr BC frequency in BTD was significantly higher than in age-matched population (7.6 vs 3.3%; p=0.006), while in females aged 30-49 yr BC frequency in BTD was higher, but not statistically significantly, than in agematched population (3.7 vs 0.5%; p=0.06). No significant difference in BC prevalence was found when patients were grouped according to the diagnosis of thyroid disorders: Graves' disease, Hashimoto's thyroiditis, nodular goiter associated or not associated with serum thyroid autoantibodies (TAb). No significant difference in BC frequency was observed between TAb+ (26/377; 6.9%) and TAb- (12/245; 4.9%) patients. The distribution of known risk factors for breast malignancies was similar in patients with or without BC.

In patients with BTD the prevalence of BC is significantly higher than the expected, showing the usefulness of screening for breast malignancy of patients with BTD.