Page 241 - Essential Haematology

Chapter 17 Acute lymphoblastic leukaemia / 227

(a) (b)

(c) (d)

Figure 17.3 Morphology, cytochemistry and immunophenotyping of acute lymphoblastic leukaemia (ALL).
(a) Lymphoblasts show scanty cytoplasm without granules. (b) Lymphoblasts are large and heterogeneous
with abundant cytoplasm. (c) Lymphoblasts are deeply basophilic with cytoplasmic vacuolation. (d) Indirect
immunofl uorescence reveals nuclear terminal deoxynucleotidyl transferase (TdT) (green) and membrane CD10
(orange). (Courtesy of Professor G. Janossy.)

tests are performed as a baseline before treatment Cytogenetics and m olecular g enetics
begins. Radiography may reveal lytic bone lesions

and a mediastinal mass caused by enlargement of Cytogenetic analysis shows differing frequencies of
the thymus and/or mediastinal lymph nodes char- abnormalities in infants, children and adults which

acteristic of T - ALL (Fig. 17.2 ). partly explains the different prognoses of these

Th e differential diagnosis includes acute myeloid groups (Fig. 17.4 ). Cases are stratified according to
leukaemia (AML), aplastic anaemia (with which the number of chromosomes in the tumour cell
ALL sometimes presents), marrow infi ltration by ( ploidy ) or by specific molecular abnormalities.

other malignancies (e.g. rhabdomyosarcoma, neu- Hyperdiploid cells have > 50 chromosomes and
roblastoma and Ewing s sarcoma), infections such generally have a good prognosis whereas hypodip-
’
as infectious mononucleosis and pertussis, juvenile loid cases ( < 44 chromosomes) carry a poor progno-

rheumatoid arthritis and immune thrombocyto- sis. The most common specific abnormality in

penic purpura. childhood B - ALL is the t(12; 21)(p13; q22) TEL -