[Soft tissue angiosarcoma in a child. Immunohistochemical and ultrastructural features].

This observation reports the case of a soft tissue tumor occurring in a 11 years-old boy. On standard histologic staining, this tumor corresponded to an undifferentiated sarcoma of high grade of malignancy. Immuno-histochemical features (laminin, vimentin, UEA I and Factor VIII R-ag) and ultrastructural analysis (presence of Weibel-Palade bodies) led us to the diagnosis of angiosarcoma. This tumor is rarely reported in children and its prognosis remains unknown. Soft tissue angiosarcoma must be differentiated from Kaposi's sarcoma, epithelioid hemangioendothelioma, hemangiopericytoma and spindle cell hemangioendothelioma. This case stresses the importance of immunohistochemical and ultra-structural features in the diagnosis of poorly differentiated vascular neoplasms.