Abstract
•Overall prognosis of uterine leiomyosarcoma (ULMS) is poor with a low 5-year survival rate.•Microsatellite instability (MSI)-high ULMS is not well documented in current literature.•Immune checkpoint inhibitors such as pembrolizumab have been shown to have good efficacy in treating MSI-high solid tumors.•Targeting MSI-high ULMS with pembrolizumab can potentially maintain a patient's quality of life and extend overall survival.