[Cystic space-occupying lesion of the neck soft tissues: cave echinococcosis].

The diagnosis of cystic echinococcosis (echinococcus granulosus) in an atypical location can be difficult to make and frequently can only be established by histological examination of affected tissues. Surgical excision and fine-needle aspiration biopsy usually lead to the diagnosis. Since puncture of these cysts may cause an anaphylactic reaction due to spillage of hydatid fluid and/or dissemination of infection, the use of fine-needle aspiration biopsy is controversial at present. We report on a patient with a cystic neck mass who developed an allergic reaction after diagnostic fine-needle aspiration biopsy. Cytological examination of the specimen was inconclusive. The allergic reaction led to the diagnosis of echinococcosis, which was confirmed by serological examination. We describe a possible diagnostic procedure for a cystic mass of unknown etiology. If imaging and serological tests are not conclusive, we believe that fine-needle aspiration biopsy is justified. However, this should only be performed in a setting that provides sufficient management for anaphylactic reactions.