Giant Intramuscular Hydatid Cyst in the Medial Thigh Compartment Treated With Wide Resection

Primary intramuscular cystic echinococcosis is rare and can resemble a soft-tissue neoplasm. A 77-year-old man presented with a six-month history of painless, progressive swelling of the medial right thigh. Magnetic resonance imaging showed a 278-mm multiloculated lesion within the vastus medialis-adductor compartment, with daughter cysts, a cyst-within-cyst appearance, and detached membranes. Thoracoabdominal imaging revealed no other focus. Albendazole was started preoperatively. The operative field was isolated with hypertonic saline-soaked pads, and the lesion was removed en bloc along the myofascial planes without cyst rupture or spillage; the cavity was then irrigated with a scolicidal agent. Histopathological examination confirmed hydatid cyst. Albendazole was continued postoperatively, and six-week magnetic resonance imaging showed no residual lesion. At 12 months, the patient was pain-free, walking independently, and had no clinically relevant hip or knee motion loss or obvious quadriceps or adductor weakness. Characteristic magnetic resonance imaging findings can prevent hazardous biopsy, while spill-free en bloc resection with scolicidal precautions can achieve local control and preserve function in selected giant intramuscular lesions.