ABSTRACT
Lymphoblastic diseases represent nearly one-third of all malignancies diagnosed in childhood and adolescence. Acute lymphoblastic leukemia (ALL) is the most common and accounts for approximately a quarter of all cancers in this age group.1-3 In contrast, non-Hodgkin lymphoma (NHL) represents the third most frequent malignancy in childhood, with the precursor lymphoblastic subtypes making up about 30 percent of cases.4-6
Lymphoblastic lymphomas (LBL) are histologically and morphologically indistinguishable from ALL, as both disorders are derived from immature precursor B or T cells. The distinction of ALL from LBL is based on the number of blasts in the bone marrow, patients with more than 25 percent blasts in the bone marrow being classified as having ALL, whereas those with fewer than 25 percent blasts in the bone marrow are classified as having LBL. Although lymphoblastic leukemia and lymphoma appear grossly identical on a mor-
sophisticated molecular-genetic studies are necessary to reveal whether they are also biologically identical disorders.
