Page 180 - Clinical Hematology Atlas

164 SECTION FOUR LEUKOCYTES

he World Health Organization classifies precursor lymphoid neoplasms into two major
Tgroups: B lymphoblastic leukemia/lymphoma and T lymphoblastic leukemia/lymphoma.
Leukemia is primarily a disease of peripheral blood and bone marrow, whereas the primary
site of involvement for lymphoma is the lymph system. Because this is an atlas of blood cells,
only the leukemia morphology will be presented. Acute lymphoblastic leukemia (ALL) is
not classified morphologically or by cytochemistry, but by a combination of cytogenetic
profiles, genotype, and immunophenotype. B lymphoblastic leukemia is subdivided into
seven subtypes that are associated with recurrent genetic abnormalities (Box 16-1). Those
cases of B-ALL that do not fall within one of these groups are classified as B lymphoblastic
leukemia, not otherwise specified. Although 50% to 70% of patients with T-ALL do have
abnormal karyotypes, none of the abnormalities is clearly associated with distinctive biologic
features, and thus T-ALL is not further subdivided.
Lymphoblasts may be either small and homogeneous or large and heterogeneous. Further
testing is needed to determine the phenotype and genotype.

BOX 16-1 B Lymphoblastic Leukemia/Lymphoma with Recurrent Genetic Abnormalities
(2008 World Health Organization Classification)
B lymphoblastic leukemia/lymphoma with t(9;22)(q34;q11.2); BCR-ABL1
B lymphoblastic leukemia/lymphoma with t(v;11q23); MLL rearranged
B lymphoblastic leukemia/lymphoma with t(12;21)(p13;q22); TEL-AML1(ETV6-RUNX1)
B lymphoblastic leukemia/lymphoma with hyperdiploidy
B lymphoblastic leukemia/lymphoma with hypodiploidy
B lymphoblastic leukemia/lymphoma with t(5;14)(q31;q32); IL3-IGH
B lymphoblastic leukemia/lymphoma with t(1;19)(q23;p13.3); E2A-PBX1 (TCF3-PBX1)
From Swerdlow SH, Campo E, Harris NL, et al, editors: WHO classification of tumours of haematopoietic and lymphoid tissues,
ed 4, Lyon, France, 2008, IARC Press.