Echinococcus infestation of the biceps brachii. A case report.

Echinococcus is a genus of tapeworm endemic in certain parts of the world but found only rarely in the United States. An extremely unusual case of an intramuscular infestation involving an extremity occurred in a 41-year-old man. Since the infestation closely resembled a soft-tissue tumor on clinical and roentgenographic examination, the patient was treated with an incisional biopsy of the mass, which consisted of a cystic cavity filled with clear fluid. The diagnosis of an Echinococcus cyst was made only after permanent section analysis revealed numerous scoleces within the cyst lining. The patient was asymptomatic six months after cyst excision but still remains at risk for recurrence of the infestation. The present report serves to alert the reader to this rare but potentially fatal condition. Preoperative diagnosis is imperative to avoid inadvertant rupture of a hydatid cyst, which releases viable scoleces into the systemic circulation and may precipitate an anaphylactic reaction.