Answer
Acute leukemias in general have a distinct lineage, either lymphoid (ie, acute lymphoblastic leukemia [ALL]) or myeloid (ie, acute myeloid leukemia [AML]). However, in a small subset of patients who present with acute leukemia, a specific lineage cannot be assigned. These cases are characterized as acute leukemias of ambiguous lineage (ALAL). [1, 2, 3]
ALALs include immature hematopoietic neoplasms that show no distinct evidence of specific lineage differentiation (ie, acute undifferentiated leukemia [AUL]) as well as leukemias that express markers of more than one lineage (ie, mixed phenotype acute leukemia [MPAL]). The MPAL further includes two subtypes: (1) those in which there is more than one malignant (blast) population, each of which represents a different lineage (formerly known as bilineal leukemia); and (2) those in which the malignant (blast) clone coexpresses lineage-specific markers (formerly known as biphenotypic acute leukemias).
-
Pathology of Acute Leukemias of Ambiguous Lineage. Blasts of acute undifferentiated leukemia.
-
Pathology of Acute Leukemias of Ambiguous Lineage. Blasts of mixed phenotype acute leukemia with t(4;11q23).
-
Pathology of Acute Leukemias of Ambiguous Lineage. Blasts of acute myeloid leukemia, type M0.
