Intramuscular Cyst in the Vastus Intermedius Muscle: A Rare Presentation of a Hydatid Cyst.

Echinococcosis, or hydatid disease, is a parasitic infection caused by a cestode from the Taeniidae family, mainly by Echinococcus multilocularis or granulosus. It is predominantly seen in the lungs or the liver. The hydatid disease rarely manifests as a palpable mass in the muscles. This study reports a case of a 70-year-old male who has presented with a swelling in the anterolateral aspect of his right upper thigh, which was progressive over the past two years. The swelling was initially painless and is now associated with pain. The clinical diagnosis of an abscess was suspected. The diagnosis of his swelling was later made as a hydatid cyst in a muscle of the thigh based on the imaging modalities, the ultrasound, and an MRI. The patient underwent surgical excision of the cyst, following which the diagnosis of a hydatid cyst was confirmed on the biopsy.