LAUSR

Laboratory and animal studies indicate that melatonin exerts a negative impact on breast cancer progression and metastasis. These actions are both receptor dependent and independent. Of the two transmembrane melatonin receptors identified in humans, breast cancer expresses only MT1. The aim of this study is to investigate the expression of MT1 in hormone receptor positive, HER2 negative invasive ductal breast carcinoma in postmenopausal women and its possible correlations with clinicopathological parameters, and survival. A total of 118 patients with Luminal A/B primary breast cancer with or without axillary metastases were identified. MT1 receptor expression was immunohistochemically assessed as percentage of stained cells and weighted index (WI) (percentage multiplied with staining intensity). Most tumor samples (84.7%) and metastasized lymph nodes (96%) stained positive for MT1, with varying intensity. No statistically significant correlations were found between MT1 expression or WI in the primary tumor and patient and tumor characteristics, or MT1 and WI in the metastasized lymph nodes. Survival analysis did not reveal a significant effect of MT1 expression or WI on risk of recurrence or survival. The role of melatonin in breast cancer is still under investigation and more research is needed to determine if and in what way could MT1 expression be used as a predictive factor in breast cancer treatment.