An unusual cause of mass in the shoulder: A primary hydatid cyst

A hydatid cyst is a zoonotic infection which may affect any organ and tissue, particularly the liver and the lung. Primary muscular hydatid cysts comprise less than 0.7-3% of the cases. The hydatid cysts must be kept in mind to avoid a diagnostic puncture in cystic lesions to avoid the spreading of the disease. In this case report, we present an exceptionally rare case with an unusual localization of a primary hydatid cyst in the left deltoid muscle.