Identifying monocytes by morphology in blood smears

Steps:

• Recall that monocytes are the largest leukocytes with a kidney-shaped or indented nucleus and abundant pale cytoplasm.
• Examine cell sizes: monocytes exceed 15 μm, larger than lymphocytes or granulocytes.
• Check nuclear shape: monocytes have a folded, horseshoe-like nucleus, unlike round or segmented ones.
• Compare cytoplasm: monocytes show gray-blue, vacuolated cytoplasm without specific granules.

Why A is correct:

• Option A matches the definition of a monocyte as the largest cell with an eccentric, indented nucleus and foamy cytoplasm.

Why the others are wrong:

• B is a lymphocyte: small size, round nucleus, scant cytoplasm.
• C is a neutrophil: multilobed nucleus, granular cytoplasm.
• D is an eosinophil: bilobed nucleus, orange-red granules.

Final answer: A