Bone marrow specimens before and after treatment with futibatinib. (A-C) Before futibatinib treatment. (A) Hematoxylin and eosin staining reveals hypercellular bone marrow (cellularity approximately >95%) (original magnification ×10). (B) A higher-magnification image of panel A shows complete myeloid maturation with increased eosinophilic forms (original magnification ×100). (C) Clusters of immature cells, most consistent with immature erythroid elements, account for ∼25% of bone marrow cellularity (original magnification ×40). (D-E) After futibatinib treatment. (D) Hematoxylin and eosin staining of the bone marrow core shows decreased marrow cellularity (∼20%) (original magnification ×20). (E) A higher-magnification image shows maturing trilineage hematopoiesis, without evidence of increased eosinophilic forms or increased pronormoblasts (original magnification ×40).