CD marker of histiocytosis is ?
**Core Concept**
Langerhans cell histiocytosis is a disorder characterized by the proliferation of Langerhans cells, a type of dendritic cell. The diagnosis of this condition often relies on identifying the specific cell surface marker expressed by these cells.
**Why the Correct Answer is Right**
The CD marker of Langerhans cells is CD1a. This marker is a glycoprotein that plays a crucial role in the presentation of lipid antigens to T-cells. Langerhans cells express CD1a on their surface, which is a key feature used to diagnose Langerhans cell histiocytosis. The presence of CD1a can be detected using immunohistochemical staining or flow cytometry.
**Why Each Wrong Option is Incorrect**
**Option A:** CD20 is a marker associated with B-cells, not Langerhans cells.
**Option B:** CD68 is a marker that is often expressed by macrophages and histiocytes, but it is not specific to Langerhans cells.
**Option C:** CD14 is a marker associated with monocytes and macrophages, and it is not specific to Langerhans cells.
**Clinical Pearl / High-Yield Fact**
When diagnosing Langerhans cell histiocytosis, it is essential to recognize the characteristic morphology of Langerhans cells, which often have a "coffee-bean" appearance. Additionally, the presence of Birbeck granules, which are rod-shaped structures within the cytoplasm of Langerhans cells, is a key diagnostic feature.
**Correct Answer: C. CD1a**