CLL is characterised by following except ?
## Core Concept
Chronic Lymphocytic Leukemia (CLL) is a type of cancer characterized by the progressive accumulation of functionally incompetent lymphocytes. It is a disorder of mature B lymphocytes. The diagnosis and characterization of CLL involve various immunophenotypic markers.
## Why the Correct Answer is Right
The correct answer can be deduced by understanding the typical characteristics of CLL. CLL cells usually express specific surface markers, including CD5, CD19, CD20, and CD23. The expression of CD5 and CD23 is particularly helpful in distinguishing CLL from other types of lymphoproliferative disorders, such as mantle cell lymphoma.
## Why Each Wrong Option is Incorrect
* **Option A:** Typically, CLL cells are positive for CD19 and CD20, which are B-cell markers. So, this option is a characteristic of CLL.
* **Option B:** CLL cells often express CD5, a marker that helps differentiate CLL from other B-cell malignancies. This is a characteristic feature.
* **Option C:** CLL cells usually express CD23, which, along with CD5, aids in the diagnosis. This is also a characteristic feature.
* **Option D:** While CLL cells can sometimes have weak or variable expression of CD20, saying CLL is characterized by "absence" might be misleading but could relate to the fact that CLL cells often have a low density of surface immunoglobulins and CD20.
## Clinical Pearl / High-Yield Fact
A key clinical pearl is that CLL is typically characterized by the presence of CD5 and CD23 on the surface of the malignant lymphocytes. This immunophenotypic profile is crucial for the diagnosis and differentiation of CLL from other lymphoid malignancies.
## Correct Answer: D.