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27

NCCN Guidelines for Patients

®

:

Acute Lymphoblastic Leukemia, Version 1.2017

3

Treatment planning

Subtypes of ALL

Doctors look at a number of factors to

plan the best treatment for you. This

includes your age, general health, and

certain features of the leukemia cells.

Some of these factors can also affect and

help predict the likely treatment outcome

(prognosis). Part 3 describes each of

these factors and how they are used to

plan treatment.

Subtypes of ALL

ALL is divided (classified) into smaller groups based

on certain features of the leukemia cells. These

smaller groups are called subtypes. The ALL subtype

is an important factor that doctors use to plan

treatment.

Cell subtypes

Doctors classify ALL into two broad subtypes

based on the type of lymphocyte the leukemia

cells come from. These are called cell subtypes.

Each type of lymphocyte can be identified by the

unique set of proteins on the surface of the cells.

The unique set and pattern of proteins is called the

immunophenotype.

There are many ALL cell subtypes based on

immunophenotype. Some are more common or more

important for treatment planning than others.

The two main cell subtypes based on

immunophenotype are described below.

†

†

B-cell ALL

– This subtype of ALL starts in

young cells that normally become mature

B-cells (B-lymphocytes). This is the most

common ALL subtype overall. Among adults

with ALL, about 75 out of 100 have B-cell ALL.

Among children with ALL, about 88 out of 100

have this subtype.

†

†

T-cell ALL

– This subtype of ALL starts in

young cells that normally become mature

T-cells (T-lymphocytes). This subtype is less

common overall, but occurs more often in

adults than in children. Among adults with ALL,

about 25 out of 100 have T-cell ALL. Among

children with ALL, about 12 out of 100 have this

subtype.

Cytogenetic subtypes

Doctors also group ALL into subtypes based on the

type of abnormal changes found in the chromosomes

of the leukemia cells. Cytogenetics is the study of

chromosomes. Thus, ALL subtypes that are based

on chromosome changes are called cytogenetic

subtypes.

Many types of chromosome changes may happen

in ALL. The Philadelphia chromosome is an

abnormal chromosome found in the leukemia cells

of some people with ALL. It is formed when parts of

chromosomes 9 and 22 break off and switch with

each other. ALL can be grouped into many subtypes

based on chromosome changes. Some are more

common or more important for treatment planning

than others.