A 62-year-old man presents with marked swelling and spontaneous bleeding of the gums. CBC shows WBC 48,000/uL with 35% large blasts having abundant gray cytoplasm and finely granular chromatin. Serum lysozyme is elevated. Bone marrow shows more than 80% monoblasts and promonocytes. Which subtype of AML is most likely?

• A Acute myelomonocytic leukemia
• B Acute myeloid leukemia with mutated NPM1
• C Acute monoblastic and monocytic leukemia ✓
• D Acute erythroid leukemia

Explanation

Monoblastic and monocytic leukemias characteristically infiltrate tissues rich in monocytes, producing gingival hypertrophy and skin involvement, with elevated lysozyme reflecting the monocytic load. In acute myelomonocytic leukemia both neutrophilic and monocytic lines proliferate, so marrow monocytic components alone do not exceed 80 percent, distinguishing it from pure monocytic leukemia here.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.