[Primary orbital cystic tumor: A case of hydatidosis in a child].

Primary orbital cystic tumors caused by Echinococcus granulosus are rare. As this parasite is endemic in Peru, we report the case of a 10-year-old girl from a rural area of Huancavelica, who presented with progressive and irreducible axial proptosis of the right eye and loss of vision. Orbital tomographic images demonstrated a tumor mass with a cystic appearance. Serologic tests were negative. The patient underwent surgical resection, and histopathologic analysis revealed anhistic membranes, corresponding to hydatid cysts. During one year of follow-up, no evidence of local or systemic recurrence was observed. In conclusion, orbital hydatidosis should be considered in the differential diagnosis of a cystic orbital tumor in pediatric patients, especially if the patient is from an endemic area.