Furthermore, the luminal A and B (estrogen receptor positive) breast cancer subtypes differ in transcriptional profiles, mutation spectra and overall survival [19]; this is in line with the clinical spectrum observed in low-grade serous ovarian cancer, with low-grade, early-stage tumors showing a favorable prognosis, while low-grade, advanced stage tumors tend to respond poorly to chemotherapy. Here, ESR1 is linked to ovarian serous adenocarcinoma.