Histiocytic Sarcoma Following B-Lymphoblastic Leukemia/Lymphoma

Area of Science:

• Hematology
• Oncology
• Genetics

Background:

• Histiocytic sarcoma (HS) is a rare malignancy.
• Clonally related HS following B-lymphoblastic leukemia/lymphoma (B-ALL) is exceptionally rare.
• Understanding the clonal relationship between B-ALL and secondary HS is crucial for treatment.

Observation:

• A patient developed HS as a breast mass 12 months after B-ALL diagnosis.
• Both malignancies shared IGH-MYC and IGK gene rearrangements.
• Whole-exome sequencing revealed common and unique mutations in B-ALL and HS, including BRAF D594G in HS.

Findings:

• The study demonstrates clonally related B-ALL and HS arise from a common precursor via divergent evolution.
• HS exhibited distinct genetic mutations compared to the precursor B-ALL.
• The BRAF D594G mutation in HS suggests a potential therapeutic target.

Implications:

• This research provides the first WES evidence of divergent evolution in clonally related B-ALL and HS.
• Identifying unique mutations in HS can inform targeted therapy development.
• Further research into the evolutionary pathways of secondary malignancies is warranted.