Successful treatment of hairy cell leukemia with TP53 abnormality using cladribine combined with low-dose rituximab: a case report and literature review.

Hairy cell leukemia (HCL) is a rare mature B-cell malignancy characterized by the BRAF V600E mutation. TP53 abnormalities in HCL are associated with poor response to standard therapies and a higher risk of relapse. We report an elderly male patient diagnosed with classical HCL (BRAF V600E-positive) who also presented with a TP53 deletion detected by fluorescence in situ hybridization (FISH) and bone marrow fibrosis. The patient was treated with one cycle of cladribine combined with low-dose rituximab (100 mg). The treatment was well tolerated. At the 7-month follow up, the patient achieved complete molecular remission, characterized by normalized blood counts, recovery of bone marrow morphology, disappearance of the TP53 deletion by FISH, negative minimal residual disease by flow cytometry, and reversal of bone marrow fibrosis from MF-2 to MF-0. This case suggests that the combination of cladribine and low-dose rituximab may be an effective therapeutic strategy for classical HCL with TP53 abnormality, enabling deep molecular response and reversal of associated bone marrow fibrosis. Further prospective studies are warranted to validate these findings.