A Rare B-Myeloid Conversion of Follicular Lymphoma into Clonally Related Acute Myeloid Leukemia: A Case Report

Follicular lymphoma (FL) is a highly prevalent indolent lymphoma, and the risk of histological transformation is approximately 2-3% per year. Transformation of FL generally occurs in the same lineage (B cell lineage). Another rare form of disease progression is the transformation of neoplastic B-cells to another cell lineage such as acute myeloid leukemia (AML). The low incidence of B-myeloid transformation associated with poor prognosis hinders the establishment of model systems to identify molecular mechanisms. A 64-year-old woman was diagnosed with FL and achieved a satisfactory response after six cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone). Approximately one month after treatment terminated, the disease progressed to AML with an increased white blood cell count and abnormal coagulation. Interestingly, nucleotide sequence analysis of the genomic region encoding the immunoglobulin heavy-chain variable domain showed the possibility of homologous transformation from lymphoma to leukemia cells. Although the patient experienced transient improvement after undergoing treatment with one cycle of idarubicin and cytarabine combined with etoposide, she relapsed and died 8 days after venetoclax salvage therapy. Patient with B-myeloid transformation was associated with an aggressive clinical course and poor prognosis. Conventional strategies for treating histologically transformed AML were ineffective. However, treatment with a Bcl-2 inhibitor could serve as an option. Here we review the literature relevant to this rare histological transformation of FL.