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Selumetinib as an Effective Therapy of Histiocytic Sarcoma Evolving From a B-Cell Acute Lymphoblastic Leukaemia
Laetitia Largeaud1,2,3,4, Charlotte Syrykh5, Julie Vial6
1Laboratory of Hematology Institut Universitaire du Cancer de Toulouse, CHU Toulouse Toulouse France.
Introduction:
Histiocytic sarcoma (HS) is a rare neoplasm derived from non-Langerhans histiocytic cells, exceptionally arising from B-ALL.
Methods:
We present the case of a child with high-risk B-ALL with PAX5 P80R mutation.
Results:
Despite initial remission, a chemoresistant paravertebral mass was identified as HS. A shared IGK/TCRB rearrangements and PAX5 alterations between the leukaemic and histiocytic clones suggested transdifferentiation driven by PAX5. A somatic MAP2K1 mutation in the HS component prompted selumetinib treatment, leading to a rapid response.
Conclusion:
This case underscores the role of PAX5 in lineage plasticity and highlights the potential of targeted MEK inhibition in MAPK-driven HS arising from B-ALL.
Trial Registration:
The authors have confirmed clinical trial registration is not needed for this submission.
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