Clonal evolution in atypical chronic granulocytic leukemia: a non-Philadelphia translocation

Area of Science:

• Hematology
• Cytogenetics
• Oncology

Background:

• Chronic granulocytic leukemia (CGL) is often associated with the Philadelphia (Ph) chromosome, a translocation between chromosomes 22 and 9.
• The emergence of a second Ph chromosome is a common indicator of the blastic phase in CGL.
• Atypical CGL cases may present unique cytogenetic abnormalities.

Observation:

• A 6-year serial study of a patient with atypical CGL revealed a specific chromosomal rearrangement: t(11;18)(q23;q12).
• This patient's marrow cells exhibited a translocation involving chromosome 18 and chromosome 11.
• Three months before blast transformation, an additional copy of the marker chromosome 18 was observed.

Findings:

• A novel cytogenetic pattern of clonal evolution in CGL was identified.
• This pattern involves a balanced chromosomal rearrangement [t(11;18)(q23;q12)] followed by duplication of the translocated chromosome 18.
• This evolution mirrors the Ph chromosome's role in CGL progression.

Implications:

• This finding presents a new cytogenetic marker for predicting blast transformation in CGL.
• Understanding these unique evolutionary patterns can aid in early diagnosis and intervention.
• Further research into atypical CGL cytogenetics may reveal new therapeutic targets.