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 32 month old female child admitted to the hospital for chief complains of productive caugh and irritability which had been progressively increased during the two weks despite the treatment. Ôn sonography:  large round 5 cm mass occupied the left side of the heart with infiltration to the adjacent lung. ÇT scan findings confirm the sonographic result. The mediastinal mass with infiltrative lung nodule was surgically removed and examined histologicallt. The typical branching and anastomosing pattern of cuboidal cells arragngement confirmed the diagnosis of an endodermal yolk sac tumor. Serial sections showed no other tissue component in this tumor. Presence of an exclusive endodermal yolk sac tumor in the mediastinum of a female child is exceptionally rare and only in a few references we could find the same tumor in a female child.