Primary hydatid cyst of vastus lateralis muscle.

Musculoskeletal system is rarely involved by hydatid cyst,the larval form of Echinococcus Granulosus. A 37-year old man was diagnosed as having a cystic mass within his left thigh musculature. Preoperative computerized tomography suggested an unusual location of echinococcus although serology could not confirm the diagnosis. During surgery, a white coloured cyst within left vastus lateralis muscle was enucleated. Pathological examination after removal of the mass revealed hydatid cyst of vastus lateralis muscle. This case emphasizes that hydatidosis should be included in differential diagnosis of any soft tissue mass especially in regions where it is endemic.