A 7-year-old boy presents with bone pain, fever, and hepatosplenomegaly. Peripheral smear shows blasts lacking granules and Auer rods. Cytochemistry shows block-like cytoplasmic positivity with periodic acid-Schiff stain and strong nuclear terminal deoxynucleotidyl transferase. The most likely lineage of these blasts is:

• A Myeloid, maturing toward neutrophils
• B Erythroid
• C Monocytic
• D Lymphoid, precursor B cell ✓

Explanation

Childhood acute lymphoblastoid leukemia typically presents with marrow failure and organomegaly. Lymphoid blasts are PAS positive with coarse block-like cytoplasmic staining and express nuclear TdT, a marker of immature lymphoid precursors; they lack Auer rods, which are specific to myeloid lineage. Monocytic and myeloid leukemias show nonspecific esterase or myeloperoxidase positivity respectively. Precursor D cell ALL expressing CD10 is the commonest subtype in children.

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.