ALL

• Mostly in kids and young adults; 80% of childhood leukemia

• Almost twice as common in whites and more common in boys

• Lymphadenopathy (from leukemic infiltration), hepatosplenomegaly (also leukemic infiltration), and infiltration of other organs (especially the brain and testicles) is common

• May have a mediastinal mass reflecting thymic involvement with T cell ALL

• Morphologic classification (FAB)

  • ALL L1

    • Homogenous population of small lymphoblasts (lymphoblasts = precursor B or T cells) with scant cytoplasm and variable basophilia

    • Nuclei are round and clefted with homogenous chromatin; inconspicuous or absent nucleoli

    • 85% of all childhood ALL

    • Often have PAS “block” positivity

  • ALL L2

    • Heterogeneously sized population of relatively large lymphoblasts with moderately abundant cytoplasm and variable basophilia

    • Multiply cleaved nuclei with prominent nucleoli and clumped chromatin

    • 15% of childhood ALL; most frequent adult ALL

    • PAS 

  • ALL L3

    • Homogenous population of intermediate sized cells (L1 <>

    • Cytoplasm is abundant, deeply basophilic, and vacuolated (vacuoles are oil red O (+))

    • Nuclei are round to oval with 1+ prominent nucleoli

    • This is a leukemic manifestation of Burkitt’s lymphoma

      • If it’s first and most prominently manifested in the blood it’s leukemia

      • If it’s first and most prominently manifested in the nodes it’s lymphoma

    • 1-2% of childhood ALL

• Immunologic classification

  • 80% are of B cell origin; those that are of T cell origin are arrested in the early intrathymic stages

  • Prognosis related to immunophenotype

    • Best with early precursor B cell ALL

    • Intermediate with immature T cell and pre-B cell ALL

    • Poorest with mature B cell ALL (ALL L3; leukemic Burkitt’s)

    • ALL in kids 2-10 YOA with early pre-B phenotype and hyperdiploidy carries the best prognosis

    • Adults (no matter phenotype) and kids with mature B phenotype have a very poor prognosis

Category: Medical Subject Notes , Pathology Notes