A 4-year-old child has pallor, easy bruising, lymphadenopathy, hepatosplenomegaly, and bone pain. Peripheral smear shows lymphoblasts. CSF examination shows 15 lymphoblasts/mm³. Immunophenotyping reveals CD10+, CD19+, TdT+ blasts. Which prognosis category does the CSF finding indicate?

• A CNS1 status — favourable; no CNS-directed treatment change
• B CNS2 status — intermediate; treatment depends on blast count threshold
• C CNS status is irrelevant if immunophenotype is favourable
• D CNS3 status — CNS disease present; requires intensified CNS therapy ✓

Explanation

CNS status classification in ALL: CNS1 = no blasts in CSF regardless of WBC count; CNS2 = <5 WBC/mm³ with blasts, or traumatic LP with blasts; CNS3 = ≥5 WBC/mm³ with lymphoblasts on cytospin, OR cranial nerve palsy, OR CNS mass lesion — indicates overt CNS disease. CNS3 disease requires intensified CNS-directed therapy (cranial irradiation is now largely replaced by high-dose intrathecal and systemic methotrexate, high-dose cytarabine). This child with 15 lymphoblasts/mm³ meets CNS3 criteria. The immunophenotype (pre-B ALL, CD10/CD19/TdT+) is separately a favourable factor for outcome but does not negate CNS3 classification.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.