Pro-T ALL: immunophenotypical analyses.

Pro-T acute lymphoblastic leukemias (ALL), also called T-I ALL, are extremely rare diseases where cells at the earliest defined stage of T-lineage maturation proliferate in the bone marrow. They are characterized by the absence of all T-lineage differentiation markers except intracytoplasmic CD3 and surface CD7. They may express markers of immaturity and a number of myeloid lineage markers, without reaching the score defining biphenotypic acute leukemia (BAL). A literature search was performed on Medline and the few publications devoted to this disorder are reviewed in this manuscript. Attempts at understanding the mechanisms leading to the development of T-I ALL, based mostly on animal experiments are further presented.