# Melatonin MT1 Receptor Expression in Luminal Invasive Ductal Breast Carcinoma in Postmenopausal Women

## TL;DR

This study examines MT1 melatonin receptor expression in breast cancer of postmenopausal women and finds no significant correlations with clinicopathological factors or survival.

## Contribution

The study provides new insights into MT1 receptor expression patterns in luminal breast cancer among postmenopausal women.

## Key findings

- Most tumor samples and metastasized lymph nodes showed positive MT1 staining.
- No significant correlations were found between MT1 expression and clinicopathological parameters.
- MT1 expression did not significantly affect recurrence risk or survival.

## Abstract

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 was 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. The MT1 receptor expression was immunohistochemically assessed as a percentage of stained cells and a weighted index (WI) (percentage multiplied by 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 the MT1 expression or the WI in the primary tumor and the patient and tumor characteristics, or the MT1 and WI in the metastasized lymph nodes. The survival analysis did not reveal a significant effect of MT1 expression or the WI on the risk of recurrence or survival.