Unexplainable development of a hydatid cyst.

Echinococcosis is a cyclozoonosis characterized by cystic lesions usually situated inside or outside the liver. We discuss the case of a 77-year-old woman with a recurrent hydatidosis with a cyst arising from the liver, growing through the lateral right abdomen wall, and reaching the subcutaneous tissue of the lumbar region. In the literature, rare subcutaneous or muscular localizations of hydatid cysts are described, however, there is no mention of a cyst growing over the abdominal wall muscles, shaped like an hourglass, partially in the liver and partially in the subcutaneous tissue, as in our case. We have not found any pathogenetic explanation for this growth pattern which is not typical of the biological behaviour of a hydatid cyst.