BACKGROUND
Primary intermuscular hydatid cyst is an exceptionally rare manifestation of Echinococcus granulosus infection, which remains a major healthcare challenge worldwide. Hydatid cysts are slow-growing masses that frequently remain undiagnosed and untreated for prolonged periods. Generally, hydatid disease is difficult to eradicate and requires long-term follow-up to ensure recurrence-free recovery. No universally accepted treatment algorithm exists for thigh hydatidosis, and treatment is individualized. Observation, pharmacologic treatment, percutaneous approaches, and surgery have been described in the literature.
CASE REPORT
We present a CE2 primary hydatid cyst measuring 18.2 cm in maximal dimension, which was located in the posterior thigh compartment of an otherwise healthy 66-year-old man involved in agricultural activities who presented with a painless mass. Contrast-enhanced computed tomography of the chest and abdomen was performed to exclude hydatid cysts at other sites. Preoperative magnetic resonance imaging raised suspicion for a hydatid cyst and facilitated surgical planning. The cyst, which was in contact with the sciatic nerve, was successfully treated via open en bloc excision and lavage, followed by a course of anthelmintic therapy. An inadvertent cyst opening occurred intraoperatively but was promptly recognized and provisionally repaired.
CONCLUSIONS
This case supports consideration of hydatid disease in selected patients with exposure-compatible, painless extremity masses; illustrates the value of advanced preoperative imaging; and demonstrates successful treatment with careful en bloc excision. The patient recovered well, without clinical evidence of recurrence or surgical complications at 15 months after surgery. Continued follow-up, including imaging for the duration recommended in the literature, is warranted to confirm long-term treatment success.

Keywords: Musculoskeletal Hydatidosis; Pericystectomy; Echinococcus Infection; Hydatid Cyst; Echinococcus granulosus