Trans-differentiation of plasma cell neoplasm to acute myeloid leukemia with monocytic features: Case report of divergent phenotype with identical genotype

Myeloid malignancies following treatment for plasma cell neoplasms (PCN) are infrequent but is a serious complication, often exhibiting complex karyotype and TP53 mutations. Plasma cell myeloma lineage switch to a myeloid malignancy with evident clonal relatedness is seldomly reported. Here, we report a unique case of acute myeloid leukemia with monocytic differentiation that shares clonal features with an antecedent plasma cell myeloma with t(4;14)(FGFR3::IGH). This phenomenon differs from therapy-related myeloid neoplasm arising from an unrelated clone and underscores the need to elucidate the role of mutations in pathways such as MAPK (e.g., BRAF and KRAS) into lineage plasticity.