PGR and breast cancer: In fact, patients with triple-negative BC (TNBC) show the highest incidence of LM (36%), with a shorter time to development of LM and OS [153,154], while LM occur approximately in 14% of patients with ER/PR-negative and HER2-positive BC and in 2.2% of patients with luminal A (low-grade and ER-positive) BC [155].