Preoperative pembrolizumab‑induced hemophagocytic lymphohistiocytosis in a patient with breast cancer: A case report

Recently, the anti-programmed cell death protein 1 antibody pembrolizumab, a type of immune checkpoint inhibitor (ICI), has been used in preoperative systemic chemotherapy for hormone receptor and human epidermal growth factor 2-negative breast cancer, also known as triple-negative breast cancer (TNBC). Chemotherapy with pembrolizumab has demonstrated clinical activity in terms of pathologic complete response and event-free survival. Despite their efficacy, the current understanding of the full spectrum of side effects associated with relatively new ICIs remains incomplete. The present study describes a case of severe pembrolizumab-induced hemophagocytic lymphohistiocytosis in a patient with early-stage TNBC, and the strategies used to manage the patient in light of their pathophysiology.