It means immature blood cell. It is a term used in Medicine and Hematology.
It's a way of calling hemogonia. From Greek 945; 953; 956; 945; ( aima "blood" ) 954; 965; 964; 959; 962; ( kytos "cell" ) 946; 955; 945; 963; 964; 959; 962; ( blastós "germ, origin" ).