Which histologic findings are characteristic of pediatric acute lymphoblastic leukemia (ALL)?

Updated: Jan 02, 2019
  • Author: Vikramjit S Kanwar, MBBS, MBA, MRCP(UK), FAAP; Chief Editor: Jennifer Reikes Willert, MD  more...
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Historically, the French-American-British (FAB) classification system allocated acute lymphoblastic leukemia (ALL) into 3 groups based on morphology, as described below. Only L3 morphology retains diagnostic relevance.

  • L1: The lymphoblast cells are usually small, with scant cytoplasm and inconspicuous nucleoli. L1 accounts for 85% of all cases of childhood acute lymphoblastic leukemia.

  • L2: The lymphoblast cells are larger than in L1. The cells demonstrate considerable heterogeneity in size, with prominent nucleoli, and abundant cytoplasm. L2 accounts for 14% of all childhood acute lymphoblastic leukemia.

  • L3: The lymphoblast cells are large with deep cytoplasmic basophilia. They frequently have prominent cytoplasmic vacuolation and are morphologically identical to Burkitt lymphoma cells. L3 accounts for 1% of childhood acute lymphoblastic leukemia cases.

See Acute Lymphoblastic Leukemia Staging for more complete information.

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