Here are subtypes of acute leukemia which are usually difficult to dignose base on bone marrow aspiration: Hypocellular acute leukemia and acute leukemia with fibrosis, often acute myeloid leukemia (acute megakaryoblastic, acute panmyelosis with myelofibrosis, acute myeloid leukemia with myelodysplasia-related changes, therapy-related myeloid neoplasms and other acute myeloid leukemia not otherwise specified).