Microangiopathic hemolytic anemia associated with radiation-induced hemangiosarcomas.

A retrospective study of red blood cell parameters in 53 dogs with experimental radiation-induced hemangiosarcoma showed 24 had anemia. Morphologic alterations in red blood cells in peripheral blood films from anemic dogs included signs of regeneration (anisocytosis and polychromasia), hypochromasia, red cell fragmentation and acanthocytosis. The degree and type of red cell changes varied from dog to dog and generally correlated with the principal site of tumor involvement. Blood from dogs with tumors principally involving liver had red cell regeneration, fragmentation and acanthocytosis. Blood from dogs with tumors primarily involving the heart had only red cell fragmentation. Blood films from dogs with skeletal and pulmonary hemangiosarcomas were similar to blood films from dogs with hepatic hemangiosarcoma except that red cell alterations generally were less severe. Scanning and transmission electron micrographic evaluation of neoplastic tissue showed large amounts of fibrin within neoplastic vascular sinuses and disruption and distortion of red blood cells traversing these abnormal vascular beds. The red blood cell fragmentation syndrome associated with radiation-induced hemangiosarcomas therefore was considered to be a microangiopathic hemolytic anemia of localized origin.