Hydatid Cyst of Skeletal Muscle Presenting as Soft Tissue Tumour.

Hydatid disease is helminthic infection caused by tape worm echinococcus granulosis. It commonly involves liver (65-75%) and the lungs (25 to 30%). Involvement of bones and skeletal muscle is very rare, i.e. 3 to 5%. This is the report of a 21-year girl, city resident, presented with mass involving left proximal thigh. The mass was painless and had gradually increased in size over three years. MRI revealed solid cum cystic lesion in vastus medialis muscle. Tru-Cut needle biopsy of the lesion revealed necrotic material. Intraoperative findings were of different sized cystic lesions, typical of hydatid cyst. The cysts were removed intact. No recurrence was seen in 11-month follow-up. Hydatid cyst involving skeletal muscle is very rare entity, but should be considered while making differential diagnosis of soft tissue mass.