**3. Diagnostic interest of chromosome Philadelphia in chronic myeloid leukemia**

#### **3.1 The chronic phase**

The Philadelphia chromosome is the only element allowing a diagnosis in hyperleukocytosis. It is found in 89 to 95% of CML cells: In the granulomonocytic,

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distinct forms:

*Research of the Philadelphia Chromosome in Chronic Myeloid Leukemia: Diagnostic…*

erythroblastic and B lymphocytic lines [3]. In most cases, CML is diagnosed on clinical and hematologic data alone. The differential diagnosis arises with all the pathologies that are accompanied by hyperleukocytosis with mild myelemia.

The almost constant presence of this translocation in CML offers clinicians an additional diagnostic tool especially in myeloproliferative syndromes (MPS), chromosome 22 can be translocated to a chromosome other than chromosome 9 or else participates in a complex translocation of most interest, often three chromosomes of which the 22 and 9 one speaks then of Ph1 variant as opposed to the standard Ph1 chromosome. This same tanslocation t(9;22)(q34;q11) is found in a non-negligible

In acute leukemia, there is an accumulation of immature precursors of the hematopoietic lineage involved in the Bonne marrow, blood, or other tissue pathologies. The acutization phase CML disease there is a significant hyperleukocytosis with the presence of the Philadelphia chromosome on all mitoses. This acutization phase is preceded by the appearance of secondary anomalies: Trisomy 8, duplication

• In 5% of acute lymphoblastic leukemia (ALL) in children and 20–30% of ALL in adults and also found in acute myeloid leukemia, In acute myeloid leukemia

Essential thrombocythemia, myeloid splenomegaly, polycythemia vera or vaquez disease and chronic myelomonocyte leukemia (CMML) have the same phenotype as show in certain forms of CM. For this reason, it is important to confirm the diagnosis of chronic myelogenous leukemia by cytogenetic study or molecular biology [5]. Sometimes to give a right diagnosis is complicated so only the karyotype or molecular biology tests can help for that. The first test looks for the presence or not of the Ph1 while the other molecular biology tests investigate the *BCR-ABL* rearrangement.

Chronic myeloid leukemia in children: There are two clinically and genetically

• The adult form occurring beyond the age of two years resembles in all respects a Ph1 + CML with the presence of the cytogenetic marker Ph1 + and break

• The juvenile form before the age of two characterized by a peculiar clinical picture and a normal karyotype in most cases otherwise the most frequent

In some cases, the Ph1 chromosome may be masked due to the size of the fragment translocated which is submicroscopic, molecular cytogenetics are then used

of Ph1, and isochromosome 17, which conditions a poor prognosis.

*DOI: http://dx.doi.org/10.5772/intechopen.95865*

• The Ph1 chromosome: Diagnoctic key

**3.2 Differential diagnosis in the acute phase**

We also find the Philadelphia chromosome:

type 1 (LAM1) and LAL1 [4].

**3.3 Other myeloproliferative syndromes**

**3.4 Chronic myeloid leukemia in children**

points in M-*BCR* especially in 5' [6, 7].

chromosomal aberration is monosomy 7**.**

percentage in ALL and AML.

*Research of the Philadelphia Chromosome in Chronic Myeloid Leukemia: Diagnostic… DOI: http://dx.doi.org/10.5772/intechopen.95865*

erythroblastic and B lymphocytic lines [3]. In most cases, CML is diagnosed on clinical and hematologic data alone. The differential diagnosis arises with all the pathologies that are accompanied by hyperleukocytosis with mild myelemia.

• The Ph1 chromosome: Diagnoctic key

*Cytogenetics - Classical and Molecular Strategies for Analysing Heredity Material*

chromosome 9 and the q11 band of chromosome 22.

is generated from the reciprocal translocation involving the q34 band of

The recent development of therapeutics targeted at the activity or stability of an oncogenic protein has recently been illustrated by the therapeutic successes obtained in the treatment of chronic myeloid leukemia and acute promyelocytic leukemia [1]. Until now cytogenetics has been the reference for structural abnormalities, in particular translocations, tools for precise diagnosis in certain disputed cases and the detection of residual diseases or possible relapses. However molecular cytogenetics can detect chromosomal abnormalities of small sizes not visible on metaphasic chromosomes (semi-cryptic). It is of particular interest in the analysis of acquired abnormalities and is involved in monitoring the persistence of an abnormal clone in order to detect predicted recurrent translocations and may also help characterize genes in the evolutionary process of carcinogenesis. The current recommendations are based on highquality evidence reported in peer-reviewed journals, supplemented by expert group consensus. These recommendations apply to healthcare professionals who treat CML patients and CML patients to better understand their conditions and treatments [2].

**2. Interest of chromosome Philadelphia in chronic myeloid leukemia**

It is the translocation of a distal fragment of the long arm of chromosome 22 (fragment 22q11.2) to the distal part of the long arm of chromosome 9 with recovery of a deleted part of the long arm of chromosome 9 on the long arm of chromosome 22. It is therefore a reciprocal translocation, without loss of chromosomal material

Since this date, we defined the standard Philadelphia chromosome as: **t(9;22)** 

**3. Diagnostic interest of chromosome Philadelphia in chronic myeloid** 

*(b) Partial RHG band karyotype of one of our patients: t(9;22)(q34;q11).*

*(a) Result of a metaphase karyotype not classified in the R-band. (the circle indicates the Ph1 chromosome).* 

The Philadelphia chromosome is the only element allowing a diagnosis in hyperleukocytosis. It is found in 89 to 95% of CML cells: In the granulomonocytic,

• The usual form or standard translocation.

**(q34;q11) or t(9; 22)(q34.1; q11.21).**

(**Figure 1(a,b)**).

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**leukemia**

**Figure 1.**

**3.1 The chronic phase**

The almost constant presence of this translocation in CML offers clinicians an additional diagnostic tool especially in myeloproliferative syndromes (MPS), chromosome 22 can be translocated to a chromosome other than chromosome 9 or else participates in a complex translocation of most interest, often three chromosomes of which the 22 and 9 one speaks then of Ph1 variant as opposed to the standard Ph1 chromosome. This same tanslocation t(9;22)(q34;q11) is found in a non-negligible percentage in ALL and AML.

## **3.2 Differential diagnosis in the acute phase**

In acute leukemia, there is an accumulation of immature precursors of the hematopoietic lineage involved in the Bonne marrow, blood, or other tissue pathologies. The acutization phase CML disease there is a significant hyperleukocytosis with the presence of the Philadelphia chromosome on all mitoses. This acutization phase is preceded by the appearance of secondary anomalies: Trisomy 8, duplication of Ph1, and isochromosome 17, which conditions a poor prognosis.

We also find the Philadelphia chromosome:

• In 5% of acute lymphoblastic leukemia (ALL) in children and 20–30% of ALL in adults and also found in acute myeloid leukemia, In acute myeloid leukemia type 1 (LAM1) and LAL1 [4].

#### **3.3 Other myeloproliferative syndromes**

Essential thrombocythemia, myeloid splenomegaly, polycythemia vera or vaquez disease and chronic myelomonocyte leukemia (CMML) have the same phenotype as show in certain forms of CM. For this reason, it is important to confirm the diagnosis of chronic myelogenous leukemia by cytogenetic study or molecular biology [5]. Sometimes to give a right diagnosis is complicated so only the karyotype or molecular biology tests can help for that. The first test looks for the presence or not of the Ph1 while the other molecular biology tests investigate the *BCR-ABL* rearrangement.

## **3.4 Chronic myeloid leukemia in children**

Chronic myeloid leukemia in children: There are two clinically and genetically distinct forms:


In some cases, the Ph1 chromosome may be masked due to the size of the fragment translocated which is submicroscopic, molecular cytogenetics are then used

#### **Figure 2.**

*The Philadelphia chromosome can be masked because of the size of the translocated fragment which is submicroscopic.*

**Figure 3.** *FISH image of* BCR/ABL *positive rearranged metaphase.*

(in situ hybridization: FISH) or real-time PCR search for the Philadelphia chromosome is necessary to confirm the diagnosis of CML and to monitor progress under certain anti-mitotic drugs (**Figure 2**)**.**

In onco-hematology, FISH provides a decisive complement to the diagnosis, the prognosis and monitoring of targeted therapies. In leukemia chronic myeloid this technique highlights the fusion of genes *BCR* and *ABL* which characterize the Philadelphia chromosome (Ph). FISH is particularly interesting in the cytogenetic monitoring of CML. In due to culture problems (low mitotic index and the quality of the metaphases poor according to European Leukemia Net 2009. This service is currently offered to patients with CML as part of the cytogenetic monitoring of their disease (**Figure 3**)**.**

#### **3.5 Variant translocations**

Variant translocations fall into two subgroups: Simple variants and complex variants; their definitions are based on the results of R, G banding and molecular biology. Although it is very common, it is quickly learned that the t(9;22) translocation is not pathognomonic for CML and it has several variants: the Ph1 (+) variants, the masked Ph1 chromosome and the Ph1 (−) variants. All chromosomes except Y are involved in the variant form of Ph1 especially chromosomes 3, 11, 12, 14 and 17 [8]. The variants can all be considered as complex translocations since the molecular genetic investigations of the supposed simple variants show that they involve at least three chromosomes and always the 9 and the 22 [9].

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*Research of the Philadelphia Chromosome in Chronic Myeloid Leukemia: Diagnostic…*

In this phase, 65 to 80% of patients develop additional chromosomal aberrations not due to chance which precede clinical and hematological manifestations by several months and which can serve as indicators prognosis [10, 11]. Secondary anomalies appear: Double chromosome Philadelphia, trisomy 8, isochromosome 17 and trisomy 19. These four additional abnormalities are part of the clonal course in 70% of CML Other, more rarely encountered anomalies seem to be due to chance, thus taking the minor pathways. In more than 50% of cases, they are represented by:

• And the translocation t(3;21)(q26;q22) which has the characteristic of being

A quarter of patients [10, 11] will not develop any additional abnormalities and

The following partial karyotypes show the association of certain additional abnormalities to the Philadelphia chromosome (Ph1) in our patients. However, the therapeutic and prognostic approach is totally different. It is therefore necessary:

• And make a differential diagnosis with myeloprolifirative and myelodysplastic

During the blast phase of CML at Ph1 (+), analysis determines as a factor of poor

prognosis [10]. As for the Philadelphia chromosome alone, it appears to have an

Evaluating the prognosis of CML using clinical-biological criteria can predict the probable date of onset of blast transformation which amounts to determining the probable duration of the chronic phase. As regards the cytogenetic criterion, it must be defined and homogeneous. The prognoses of Ph1 (+) CML and Ph1 (−) CML should be studied separately because we have seen the current difficulties of

In our medical genetics' laboratory. The suspected diagnosis was CML in 69

**4. Prognostic interest of chromosome Philadelphia in CML**

including the Ph1 (−) form in the nosological framework of CML.

patients, unlabeled SMP in the remaining 22 patients (**Table 1**).

• Philadelphia chromosome or t(9;22)(q34;q11) in 60 cases.

*DOI: http://dx.doi.org/10.5772/intechopen.95865*

**3.6 The blast transformation**

• Monosomies: Y, 7, 17.

• Down's syndrome: 17 and 21.

accompanied by medullary fibrosis [12].

Make a positive diagnosis for CML.

• Specify the evolutionary stage.

independent prognostic value [13].

• Culture failure in 6 cases.

• Normal karyotype in 25 cases.

syndromes.

will keep Philadelphia alone for the duration of their survival.

**3.7 Chronic myeloid leukemia with secondary abnormalities**

• Correct the diagnosis of certain contentious cases.

*Research of the Philadelphia Chromosome in Chronic Myeloid Leukemia: Diagnostic… DOI: http://dx.doi.org/10.5772/intechopen.95865*
