Hydatidosis (echinococcosis)  is a  parasitic  infection  in  human . The

   most common cause of hydatid cyst is echinococcus granulosus.

         Hydatid cysts commonly involve the liver,lungs and rarely other organs

   as spleen , pancreas and breast.

         The  patient of this case - report  was a 17 years old girl that referred to

   hospital  with  a  slowly growing  mass  in her right breast occasionally with

   pain  sensation  from  one  month  before referring to clinic. She operated

   and  observed  a  cystic  mass  with  doughter  cyst  and  clear  fluid.  Cyst

   excised completely .

         The pathological study confirmed the diagnosis of a hydatid cyst.