Question:hard
All of the following immunohistochemical markers are positive in the neoplastic cells of granulocytic sarcoma, except:
All of the following immunohistochemical markers are positive in the neoplastic cells of granulocytic sarcoma, except:
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Three options are myeloid markers; which one is a T-cell marker?
Updated On: Jun 24, 2026
- CD45 RO
- CD43
- Myeloperoxidase
- Lysozyme
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Identify the tumour. A chloroma (granulocytic sarcoma, myeloblastoma) is a tissue mass of leukaemic myeloblasts seen outside the marrow, typically in AML with monocytic features. The classic green colour comes from myeloperoxidase in the blasts.
Step 2: Predict its immunophenotype from lineage. Being myeloid, the cells light up for myeloid and histiocytic markers: myeloperoxidase, lysozyme, CD43, plus CD68, CD117 and CD34. Three of the four options listed (CD43, myeloperoxidase, lysozyme) fall squarely in this myeloid panel.
Step 3: Spot the odd one out. CD45 RO is a T-lymphocyte associated isoform, used to mark T cells, not myeloid blasts. It does not belong to the granulocytic sarcoma profile.
Step 4: The question asks which marker is NOT positive, so the exception is CD45 RO.
\[\boxed{\text{CD45 RO}}\]
Step 2: Predict its immunophenotype from lineage. Being myeloid, the cells light up for myeloid and histiocytic markers: myeloperoxidase, lysozyme, CD43, plus CD68, CD117 and CD34. Three of the four options listed (CD43, myeloperoxidase, lysozyme) fall squarely in this myeloid panel.
Step 3: Spot the odd one out. CD45 RO is a T-lymphocyte associated isoform, used to mark T cells, not myeloid blasts. It does not belong to the granulocytic sarcoma profile.
Step 4: The question asks which marker is NOT positive, so the exception is CD45 RO.
\[\boxed{\text{CD45 RO}}\]
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