Page 79 - New epidemiological and PSMA-expression based paradigms in salivary gland tumors

Risk of breast cancer after a salivary gland tumor in the Netherlands
Introduction
Major salivary gland cancer (SGC) and salivary gland pleomorphic adenoma (SGPA) together constitute almost three quarters of all salivary gland tumors, and have a yearly incidence of respectively 0.7 and 4.9/100,000 person-years in the Netherlands (European Standardized Rate)[1,2]. Benign salivary gland tumors occur 6-7 times more frequently than malignant tumors and the SGPA, which accounts for two thirds of all benign salivary gland tumors, may occasionally show malignant transformation[2–6].
Salivary and mammary gland tumors show morphological similarities and salivary gland-like type tumors have been described in the breast[7–11]. They also share other characteristics, including frequent overexpression of hormone receptors and in some histologies a female preponderance, most consistently in salivary gland adenoid cystic carcinoma and SGPA[1–3,12–16].
Whereas the larger amount of glandular breast tissue (next to hormonal, lifestyle, and genetic factors) puts women at higher risk of BC than men, gland volume does not explain the higher risk of a salivary gland tumor in women, since there are no gender differences in salivary gland size[17]. Differential attitudes towards physical appearance or towards medical attention seeking behaviour between males and females are unlikely to play a major role in explaining gender variation in incidence of SGC and SGPA, due to visibility of the tumor[18–20].
Although the similarities may suggest a common etiology, it remains uncertain whether patients with a salivary gland tumor carry an increased risk of breast cancer (BC). Literature is inconclusive regarding whether risk is increased, and if so, to what extent and in which patients. A previous salivary gland tumor as a risk factor for BC has been reported in the literature, but studies are ambiguous, possibly due to the variation in sample size and inclusion criteria[21–28]. Support for a hormonal component in salivary gland cancer risk was earlier reported in an epidemiological study, and a hormonal influence could also have played a role in the recently reported higher risk of SGC in women after BC[29,30].
The objective of this study was to determine whether women diagnosed with a SGC or SGPA have an increased risk of developing BC in two nationwide population- based cohorts with long term follow-up and complete cancer incidence data.
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