Which of the following is not compatible with a diagnosis of chronic myelomonocytic leukemia?
**Core Concept**
Chronic myelomonocytic leukemia (CMML) is a type of myelodysplastic/myeloproliferative neoplasm characterized by a clonal proliferation of myeloid cells in the bone marrow, leading to an increased number of monocytes and granulocytes in the peripheral blood. The diagnosis of CMML is based on a combination of clinical, morphological, and immunophenotypic features.
**Why the Correct Answer is Right**
CMML is typically characterized by a gradual increase in the number of monocytes and granulocytes in the peripheral blood, often accompanied by anemia, thrombocytopenia, and splenomegaly. The bone marrow is usually hypercellular, with a mixture of mature and immature myeloid cells. In contrast, acute myeloid leukemia (AML) is a more aggressive disease characterized by a rapid increase in the number of immature myeloid cells in the peripheral blood and bone marrow.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because CMML is often associated with anemia and thrombocytopenia, which are not typically seen in AML.
**Option B:** This option is incorrect because CMML typically presents with a gradual increase in the number of monocytes and granulocytes, whereas AML presents with a rapid increase in the number of immature myeloid cells.
**Option C:** This option is incorrect because CMML is characterized by a mixture of mature and immature myeloid cells in the bone marrow, whereas AML is characterized by a predominance of immature myeloid cells.
**Option D:** This option is incorrect because CMML often presents with splenomegaly, which is not typically seen in AML.
**Clinical Pearl / High-Yield Fact**
CMML often presents with a gradual increase in the number of monocytes and granulocytes in the peripheral blood, which can be mistaken for a benign reactive process. Therefore, a careful evaluation of the bone marrow and peripheral blood smear is essential for making a diagnosis of CMML.
**Correct Answer: D. AML. Acute myeloid leukemia.**