Résumé
Ultrastructural study of five cases of choriocarcinoma out of the examined cases of trophoblastic disease revealed biphasic cytotrophoblast [CT] and syncytotrophoblast [ST] structure. CT cells were characterized by electronic light cytoplasm containing scattered rough endoplasmic reticulum [RER]. The nucleus had oval contour and prominent nucleoli. ST cells showed complex electronic dense cytoplasm containing abundant RER, free ribosomes and lipid droplets. More than one nucleus were present with irregular outlines and coarse clumped chromatin. Two cases of placental site trophoblast tumor [PSTT] were studied ultrastructurally showing prominent intermediate trophoblast [IT] cells characterizing by irregular hyperchromatic nucleus with complex cytoplasm with dilated RER and paranuclear tonofilaments. The ultrastructural study of these lesions gave a perfect diagnostic differentiation between them