The connection between genetic liability to endometriosis and melanoma is difficult to explain physiologically, although Yang et al. (2021) notes that melanocytes express oestrogen receptors (ER) and oestrogen is believed to play a role in melanoma (Mori et al., 2006; Schmidt et al., 2006; Koomen et al., 2009; Marzagalli et al., 2015; Yang et al., 2021). Here, ESR1 is linked to endometriosis.