Which of these is true regarding CML -a) Size of splenomegaly indicates prognosisb) Phagocytic activity of WBC is reducedc) Sudan black stain is specific for myeloblastd) Myeloblast, granuloblast and lymphoblast are PH chromosome +ve.

**Core Concept**
Chronic myeloid leukemia (CML) is a type of cancer characterized by the uncontrolled proliferation of mature granulocytes, primarily neutrophils, in the bone marrow. The disease is associated with a chromosomal abnormality known as the Philadelphia chromosome, resulting from a reciprocal translocation between chromosomes 9 and 22. This translocation creates a fusion gene, BCR-ABL, which encodes a constitutively active tyrosine kinase that drives the leukemic cell growth.

**Why the Correct Answer is Right**
The size of splenomegaly is indeed an indicator of prognosis in CML. As the disease progresses, the spleen becomes enlarged due to the accumulation of leukemic cells, leading to a significant increase in its size. This is often a reflection of the disease's severity and may correlate with a poorer prognosis. In contrast, options B and C are incorrect as phagocytic activity of WBC is not reduced in CML and Sudan black stain is not specific for myeloblasts. Option D is also incorrect as myeloblasts, granuloblasts, and lymphoblasts are not necessarily PH chromosome positive; this characteristic is specific to CML.

**Why Each Wrong Option is Incorrect**
**Option A:** While splenomegaly is indeed a feature of CML, it is not the only indicator of prognosis. Other factors, such as the presence of blast cells in the peripheral blood and the degree of bone marrow fibrosis, also play a role in determining the disease's prognosis.

**Option B:** Phagocytic activity of WBC is not reduced in CML. In fact, the leukemic cells in CML are often mature and functional, and their phagocytic activity is typically preserved.

**Option C:** Sudan black stain is not specific for myeloblasts. It is a general stain that can be used to identify various types of cells, including myeloblasts, but it is not a specific marker for these cells.

**Option D:** Myeloblasts, granuloblasts, and lymphoblasts are not necessarily PH chromosome positive. This characteristic is specific to CML and is not a feature of other types of leukemia.

**Clinical Pearl / High-Yield Fact**
The Philadelphia chromosome is a hallmark of CML and is present in over 90% of cases. This chromosomal abnormality is a result of a reciprocal translocation between chromosomes 9 and 22 and is responsible for the development of the leukemic cells.

**Correct Answer:** .