In simple words: Atypical chronic myeloid leukemia (aCML) is a rare blood and bone marrow cancer where the bone marrow produces too many abnormal white blood cells. It's different from typical CML because it lacks a specific genetic marker.It often causes symptoms like fatigue, easy bruising, and frequent infections.

Atypical chronic myeloid leukemia (aCML), BCR/ABL-negative, is a rare myelodysplastic/myeloproliferative neoplasm (MDS/MPN) characterized by leukocytosis, prominent dysgranulopoiesis, and granulocytic dysplasia, without the BCR-ABL1 fusion gene. It primarily affects the neutrophil series, often presenting with anemia, hepatosplenomegaly, and a high risk of transformation to acute myeloid leukemia.

Example 1: A 75-year-old patient presents with fatigue, easy bruising, and frequent infections. Blood tests reveal anemia and thrombocytopenia. Bone marrow biopsy confirms the diagnosis of aCML, BCR/ABL-negative., A patient with a history of MDS/MPN is found to have increased leukocytosis with immature granulocytes. Genetic testing is negative for BCR-ABL1, and a diagnosis of aCML is made., A patient with suspected CML undergoes testing, and the Philadelphia chromosome is absent. Further evaluation reveals dysgranulopoiesis and dysplasia, leading to a diagnosis of aCML.

Documentation should include complete blood count (CBC) results, bone marrow biopsy findings, cytogenetic analysis confirming the absence of BCR-ABL1 fusion gene, and any other relevant diagnostic tests performed (e.g., FISH, PCR, flow cytometry, imaging). Clinical findings such as hepatosplenomegaly, anemia, and thrombocytopenia should also be noted.