Anaplasia rediviva.

Anaplasia refers to the apparent retrogression toward an embryonic state that occurs in some human and animal tumors, the consequence, presumably, of a derepression of genes that would normally have been switched off in the course of development. The fetal substances newly formed in tumors are identified immunologically and are therefore referred to as "antigens." Some such antigens, for example, carcinoembryonic antigen and alpha-fetoprotein, and blood-group precursor substances have great promise diagnostically but play no known part in resistance to malignant growth. The reawakened fetal antigens that are of special interest and importance are those that are capable of arousing cell-mediated immunity and thus may contribute to antitumor immunity. Modern research, therefore, rehabilitates an etiologc notion earlier thought to have been discredited.