Rare case of human epidermal growth factor receptor 2-positive gastric remnant cancer after bariatric surgery—case report

Summary Parallel to the increasing number of patients with obesity and metabolic syndrome, the number of bariatric procedures is rapidly growing. Gastric bypass is the surgery of choice due to its high efficiency and safety profile; however, subsequent assessment and surveillance of the excluded stomach poses considerable challenges. Gastric remnant cancer is a rare entity and only a few cases have been published in the literature. Here, we report the first case of a human epidermal growth factor receptor 2-positive gastric cancer in the excluded remnant in a 58-year-old man with a history of bariatric Roux-en‑Y gastric bypass surgery. This case highlights the challenge of cancer surveillance in the eliminated stomach and chemotherapeutic treatment after bariatric surgery. Furthermore, we address the efficacy of trastuzumab deruxtecan as a second-line therapy in HER2-positive gastric cancer.