Primary hydatid cyst of skeletal muscle: A rare clinical entity.

Introduction: Hydatid cyst is a parasitic infection caused by Echinococcus granulosus, commonly affecting the liver and lungs. Muscular involvement is extremely rare, accounting for only 0.7 % to 0.9 % of cases. This case highlights the diagnostic challenges of muscular hydatid cysts, which can mimic sarcomas, abscesses, or lipomas.

Case Report: A 90-year-old female from a rural area presented with a slow-growing swelling on the posteromedial thigh for three years. She had no history of trauma or systemic symptoms. Clinical examination revealed a firm, non-tender mass. Imaging suggested a cystic lesion, and serology confirmed Echinococcus infection. Surgical excision was performed, and histopathology confirmed a hydatid cyst. The patient received a six-week course of albendazole postoperatively. Her recovery was uneventful, with no recurrence at follow-up.

Discussion: Muscular hydatid cysts are rare and often misdiagnosed as soft tissue tumors. Imaging modalities, particularly ultrasound and MRI, aid in diagnosis, while serology provides further confirmation. Complete surgical excision remains the preferred treatment, and antiparasitic therapy reduces recurrence risk.

Conclusion: Although rare, muscular hydatid cysts should be considered in the differential diagnosis of soft tissue swellings, particularly in endemic regions. Early recognition and appropriate management prevent complications and improve patient outcomes.