PGR and breast cancer: Kisspeptin 1 receptor mRNA expression was higher in women with advanced stages of BC (stage III) than in BC patients showing stage II; a correlation was reported between kisspeptin 1 receptor mRNA expression and lymph node metastasis and tumor size; kisspeptin 1 receptor mRNA expression was more highly expressed in estrogen receptor-negative cases than in estrogen receptor-positive subjects and in progesterone receptor-negative cases than in progesterone receptor-positive ones [120].