Internal Medicine

0521779407-01 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 20:45

Acute Lymphoblastic Leukemia 31

(2) Mature B-ALL characterized by expression of surface immuno-

globulin sIgM, and cytoplasmic kappa or lambda light chains

(this is the former L3 variant or Burkitt’s leukemia)

(3) T-lineage ALL characterized by expression of cyCD3 or sCD3.

Subsets of T-cell ALL include pro-T-ALL (CD7+), pre-T-ALL

(CD2+, and/or CD5+, and/or CD8+), cortical T-ALL (CD1a), and

mature T-ALL (sCD3+, CD1a−). Immunophenotypic classifica-

tion of ALL has importance for prognosis & treatment.

■Morphologic features of lymphoblasts are important: presence of

condensed nuclear chromatin, evaluation of nuclear to cytoplasmic

ratio, absence of Auer rods and granules in the cytoplasm are con-

sistent with diagnosis of ALL.

■Morphologically distinct lymphoblasts in the uncommon (∼5%)

mature B-ALL sub-type ALL- L3 (relatively homogeneous, medium

size, more dispersed chromatin, multiple nucleoli, deep blue cyto-

plasm with sharply defined vacuoles); these cells are also often TdT

negative.

■Characterize the abnormal peripheral blood cells (Wright stain, mor-

phology, complete immunophenotypic analysis); important to also

include cytogenetics and molecular genetic studies

Basic Bone Marrow Testing:

■Bone marrow aspirate and biopsy examinations include cytochemi-

cal and special stains to define the type of acute leukemia infiltrating

the marrow (morphologic features, Wright stains) and assessment

of normal marrow cells remaining (e.g., red cell and megakaryocyte

preservation); specialized stains to define the type of blasts include

(at minimum): myeloperoxidase negative; usually PAS glycogen pos-

itive in block pattern; terminal deoxynucleotidyl transferase (TdT)

positive (except L3), but the PAS & TdT can also be observed in small

number of AML cases. Therefore, PAS & TdT not exclusively diag-

nostic of ALL. However, the use of immunophenotypic analysis has

become extremely important in defining the final diagnosis.

■Bone marrow aspirate collected in anticoagulant should also be sent

for flow cytometric full immunophenotypic characterization and

molecular analyses.

■Bone marrow aspirate in a sterile vial MUST also be sent for cyto-

genetics. However, FISH probes are now available for major cytoge-

netic abnormalities. FISH analysis does not require cells to undergo

division.

■Bone marrow biopsy is important to define fibrosis and cellularity