While analysis of the case-controlled prospective Nurses' Health Study cohort of 851 patients found no difference in relative risk for postmenopausal breast cancer in ductal vs lobular cancer with elevated PRL plasma levels [26], our more recent data using a population-based case-controlled study of 773 women from Poland has shown that serum PRL levels were significantly higher in post-menopausal women with invasive lobular compared to ductal carcinoma [27]. Here, PRL is linked to breast cancer.