Monosomy 20 as a pointer to dicentric (9;20) in acute lymphoblastic leukemia

Area of Science:

• Hematology
• Cytogenetics
• Oncology

Background:

• Acute lymphoblastic leukemia (ALL) is a heterogeneous hematologic malignancy.
• The dicentric chromosome dic(9;20)(p1113;q11) is a rare chromosomal abnormality observed in ALL.
• Standard G-banding techniques can misinterpret dic(9;20) as monosomy 20, hindering accurate diagnosis.

Purpose of the Study:

• To identify and characterize new cases of ALL with the dic(9;20) chromosomal abnormality.
• To evaluate the diagnostic utility of fluorescence in situ hybridization (FISH) for detecting dic(9;20).
• To investigate the clinical and cytogenetic associations of dic(9;20) in ALL patients.

Main Methods:

• Retrospective analysis of 20 new cases of ALL with suspected dic(9;20).
• G-banding and fluorescence in situ hybridization (FISH) were used for chromosomal analysis.
• Review of the Leukaemia Research Fund/UK Cancer Cytogenetics Group Karyotype Database for cases with monosomy 20.

Main Results:

• Twenty new cases of ALL with dic(9;20) were identified, increasing the total reported cases to 37.
• FISH confirmed dic(9;20) in 20 out of 25 cases initially suspected of having monosomy 20.
• Eight of the 20 patients with dic(9;20) also exhibited trisomy 21. One case of T-ALL with dic(9;20) was identified.

Conclusions:

• The dicentric chromosome dic(9;20) is an under-recognized abnormality in ALL that requires FISH for accurate identification.
• dic(9;20) is associated with specific immunophenotypes and can co-occur with trisomy 21.
• Accurate cytogenetic diagnosis of dic(9;20) is essential for understanding its role in ALL pathogenesis and prognosis.