In 2018, Stover et al., using targeted next-generation sequencing (NGS), detected a Y537S ESR1 mutation in one patient with low-grade serous ovarian cancer (LGSOC); this particular patient developed a single site of progressive disease in an abdominal wall nodule and maintained stable low-volume peritoneal disease during endocrine therapy for almost five years, but later presented progressive disease after a durable response to hormonal therapy [32]. The gene discussed is ESR1; the disease is disease of peritoneum.