Abstract
Salivary and mammary gland tumors show morphological similarities and share various characteristics, including frequent overexpression of hormone receptors and female preponderance. Although this may suggest a common etiology, it remains unclear whether patients with a salivary gland tumor carry an increased risk of breast cancer (BC). Our purpose was to determine the risk of BC in women diagnosed with salivary gland carcinoma (SGC) or pleomorphic adenoma (SGPA). BC incidence (invasive and in situ) was assessed in two nationwide cohorts: one comprising 1567 women diagnosed with SGC and one with 2083 women with SGPA. BC incidence was compared with general population rates using standardized incidence ratio (SIR). BC risk was assessed according to age at SGC/SGPA diagnosis, follow-up time and (for SGC patients) histological subtype. The mean follow-up was 7.0 years after SGC and 9.9 after SGPA diagnosis. During follow-up, 52 patients with SGC and 74 patients with SGPA developed BC. The median time to BC was 6 years after SGC and 7 after SGPA. The cumulative risk at 10 years of follow-up was 3.1% after SGC and 3.5% after SGPA (95% Confidence Interval (95%CI) 2.1%-4.7% and 2.6%-4.6%, respectively). BC incidence was 1.59 times (95%CI 1.19-2.09) higher in the SGC-cohort than expected based on incidence rates in the general population. SGPA-patients showed a 1.48 times (95%CI 1.16-1.86) higher incidence. Women with SGC or SGPA have a slightly increased risk of BC. The magnitude of risk justifies raising awareness, but is no reason for BC screening.