Hidden hydatid: shoulder cyst mistaken for benign bump

This case report describes a 29-year-old man with a rare parasitic cyst in his shoulder muscle that was initially mistaken for a common synovial cyst. After incorrect treatment with steroids caused inflammation, doctors correctly diagnosed it through imaging and surgery. The patient recovered fully after surgical removal and three months of medication. The report aims to help doctors consider this rare infection in muscle locations, especially in regions where the parasite is common.