RHABDOMYOSARCOMA OF THE URACHUS - A CASE-REPORT

BACKGROUND: Rhabdomyosarcoma of the urachus is extremely rare, and onl y two cases have been reported. Cytologic, histologic, immunochemical and electron microscopic-findings in embryonal rhabdomyosarcoma of the urachus are presented. CASE: Embryonal rhabdomyosarcoma of the urachu s developed in a 2-year-old boy. Imprint smears prepared prior to a hi stologic examination for a rapid report contained many malignant cells isolated or in clusters in a myxoid background. They were uniformly s mall, with round to oval nuclei and scant cytoplasm, and immunohistoch emically positive for desmin and alpha-sarcomeric muscle actin but neg ative for myoglobin. This tumor was diagnosed cytologically as embryon al rhabdomyosarcoma because of its skeletal muscle origin and because of its similarity to one of the so-called small round cell tumors of c hildhood. Histologic examination confirmed the cytologic diagnosis. CO NCLUSION: Cytologic, histologic and electron microscopic findings were identical to, those described previously for embryonal rhabdomyosarco ma at other sites. In immunochemical examinations, cytologic samples f ixed in ethanol are more useful than histologic ones fixed in formalin . That, in order to differentiate poorly differentiated rhabdomyosarco ma from other small round cell rumors in children, desmin and alpha-sa rcomeric actin, rather than myoglobin, are recommended.