[ Home Page ]�[ Site Map ]

1. Tumours of Precursor Lymphoid Cells

Lymphoblastic leukaemias. Diagnosis requires demonstration of a neoplastic population with immunophenotype of precursor T or B-cells. The term lymphoblastic leukaemia will be used for all cases irrespective of pattern of disease.

• 1.1 Precursor B-lymphoblastic Leukaemia
• 1.2 Precursor T-lymphoblastic Leukaemia

1.1 Precursor B-lymphoblastic Leukaemia

Diagnostic Criteria

Typical Cases:

1. Bone marrow or solid tissue infiltration with blast cells
2. Immunophenotype: CD19⁺,CD22⁺,Tdt⁺,CD117^-,cCD79α⁺,cCD3^-, cMPO^-, CD34^var,CD45^wk

Variants:

1. CD10 and cytoplasmic µ heavy chain define common and pre-B subtypes according to traditional criteria. These distinctions are of no clinical value.
2. Bcr-abl associated phenotype: CD34-homo⁺⁺⁺,CD10-homo⁺,CD13⁺ and/or CD33⁺,CD38^wk/-
3. t(12;21) associated: common ALL phenotype with CD10-hetero⁺,CD13⁺ and/or CD33⁺
4. t(4;11) associated in infancy: NG2⁺,CD10^-,CD15⁺,CD19⁺,CD22⁺. All CD10^- infant acute leukaemias require full myeloid panel. These cases are reported as t(4;11)-associated acute leukaemia

1.2 Precursor T-lymphoblastic Leukaemia

Diagnostic Criteria

Typical Cases:

1. Bone marrow or solid tissue infiltration with blast cells
2. Immunophenotype: CD19^-,Tdt⁺,cCD3⁺,CD2⁺,CD7⁺,CD22^-,MPO^- (by flow)

Variants:

1. CD1a expression defines common thymocyte type
2. CD13 or CD10 expression may be seen but is of uncertain clinical significance
3. Weak sCD3 or TCR or cCD79a or CD117 may be seen in some cases

Terms to be used

Definition of Remission Status

When a blast cell population with a leukaemia-associated phenotype is detected unequivocally by flow cytometry on the basis of patterns of CD34, CD19, CD20 and CD10 expression or PCR this will be reported as not in remission, with the extent of infiltration stated. Where these techniques are not available remission will be defined as a morphological blast cell count of <5%.

Terms to be used

[Home Page ]�[Site Map ]