Early T-cell precursor acute lymphoblastic leukemia with KRAS and DNMT3A mutations and unexpected monosomy 7.

Early T-cell precursor acute lymphoblastic leukemia/lymphoma (ETP-ALL) is a recently recognized subgroup of T lymphoblastic leukemia/lymphoma thought to be derived from lymphocytes at the ETP differentiation stage that have not irreversibly committed to the T-cell lineage. The definition of ETP-ALL is based on a unique immunophenotype that also expresses at least one myeloid or stem cell marker other than myeloperoxidase and monocytic markers. Correspondingly, ETP-ALLs are often found to express myeloid-associated mutations and have stem cell gene expression profiles. Because its morphology is nonspecific, recognizing the immunophenotype of this uncommon entity is important to separate it from other closely related acute leukemias. We report a case of ETP-ALL with KRAS and DNMT3A mutations and monosomy of chromosome 7 that did not initially respond to conventional ALL therapy but eventually responded to acute myeloid leukemia-type therapy, underscoring the interesting characteristics of this leukemia. Little information is available regarding monosomy 7 in this entity for the adult population.