Acute lymphoblastic leukemia (ALL)

ALL: Rapid growth of abnormal white blood cells impairing normal blood cell production; requires prompt treatment like chemotherapy.

Leukemia is the most prevalent childhood cancer, with acute lymphoblastic leukemia (ALL) representing 75-80% of cases.

FAB Classification of ALL

L1: Mature-appearing lymphoblasts, small blasts, high N:C ratio.

L2: Immature and pleomorphic lymphoblasts, small and large blasts, moderate N:C ratio.

L3: Large and uniform lymphoblasts (Burkitt's cells), deep basophilic cytoplasm, vacuolation, low N:C ratio.

Features	L1	L2	L3
Cell size	Small, uniform	Large, often heterogeneous	Large, homogeneous
Nucleus	Round, regular	Oval to round, irregular clefting	Round
Amount of cytoplasm	Scant	Moderately abundant	Moderately abundant
Genetic material	Dense, uniform	variable	finely stippled and uniform
Nucleoli	Inconspicuous, small	Prominent, large 1 - >1	Present, may be prominent, 1- >1, vesicular
cytoplasm vacuoles	Occasional	Variable	Prominent
Basophilia	Slight	Variable	Punctate
Frequency	85%	15%	2%

WHO Classification of ALL:

1. Precursor B-cell ALL/LBL:

- B-ALL: 85% of childhood ALL, predominant in bone marrow.

- B-LBL: Rare lymphoma, 10% of lymphoblastic lymphoma cases.

- T-ALL: 15-20% of childhood ALL, predominant in adolescents, more in males.

- T-LBL: Lymphoma with primary lymph node or extranodal involvement.

B-ALL: Bone marrow predominance, sometimes lymph node or extranodal involvement.

T-ALL: Pre-T markers, more common in adolescents and males, often L2 morphology.

1. Cytochemistry: Identifies chemical components of cells for leukemia classification.

2. Biochemical Tests: Elevated serum uric acid, LDH, hypocalcemia, hyperuricemia, increased potassium.

3. Imaging Studies: X-rays, CT scans, MRI, radionuclide imaging, ultrasound to detect organ invasion.

4. CSF Examination: Looks for blast cells in cerebrospinal fluid.

5. Karyotyping: Examines chromosome complement for cytogenetic analysis.