**5.2 Trisomy 8**

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

disease may dictate which therapy is most appropriate (**Figure 2**).

considered as specific to MDS if the clinical context is appropriate.

**5. Cytogenetics**

not del(7q).

del(5q), +8, del(20q), and − 7 [10, 11].

the cytogenetic response after treatment.

lineage can be hypoplastic.

the allele 5q normal.

**5.1 The deletion of 5q and "5q- syndrome"**

months, years, or decade) and is important to define treatment strategy.

implications of specific cytogenetic abnormalities on the Revised International Prognostic Scoring System (IPSS-R). In addition, the genetic profile of a patient's

In fact, risk stratification in the first step in the care of newly diagnosed MDS is crucial, it help to convey disease severity, can set expectations (overall survivor for

Conventional prognostic scoring of MDS is based on the extent of cytopenia, the percentage of bone marrow blast infiltration, and karyotype abnormalities [8, 9]. Metaphase cytogenetic show presence of abnormalities in approximately 50% of MDS. Some of cytogenetic abnormalities are characteristic of MDS, they may be

Only del(5q) may be considered as MDS subtype. Therefore, the 2016 revision of the WHO classification considered cases with del(5q) plus one other abnormality to be categorized as MDS with isolated del(5q), providing the second abnormality is

Acute myeloid leukemia (AML) is characterised by balanced abnormalities wich predominate, in contrast of MDS where unbalanced abnormalities are more common. Overall, the most frequent abnormalities are loss of the Y chromosome (-Y),

Thus, a constitutional karyotype on a blood sample cultivated using phytohemaglutin like a mitogen can be realised in these two cases for a right interpretation of

On the other hand, cytogenetic abnormalities are more frequent in therapyrelated MDS (t-MDS) than de novo MDS, being reported in 70–90% cases [12].

The interstitial deletion of the long arm of chromosome 5 (del (5q)), can be considered the most frequent cytogenetic aberration in MDS, it occurs in 15% of patients with MDS. The "5q syndrome" is defined by an isolated del (5q) and an absence of excess blast, on the peripheral blood or the marrow. The IPSS includes a patient with del (5q) isolated in a favorable group. These patients have distinct morphological characteristics, thrombocytosis is found in one third of patients, macrocytic anemia and hypolobulated megakaryocytes, on the other hand, showed little dysplasia along the granulomonocytic and erythroid lines. The erythroid

The prognosis is favorable, overall survival for patients with 5q- is prolonged and the risk of progression to AML is lower than other patients with MDS. Even without treatment, clonal evolution is rarely reported. The prognosis is indeed dominated by the consequences of chronic transfusions, but these patients respond

The 5q suppression can vary in size, but invariably affects bands q31 to q33. A common 5q33 deletion spanning more than 1.5 Mb and encompassing 42 genes has been reported. A model of haploinsufficiency in which the loss of a single copy of one or more genes possibly responsible for the 5q syndrome is suggested, and this may be explained by the absence of recurrent point mutation or cryptic deletion on

dramatically to the immunomodulating agent lenalidomide [13].

The National Comprehensive Cancer Network (NCCN) guidelines stratify patients on low and high risk patient with different treatment options (**Figure 3**).

**120**

Trisomy 8 + 8, (10–15%) that sometimes results from germinal mosaicism, is often subclonal, fluctuating independently of blast counts.
