#00060890

This is the CSF smear of a 19-year-old male with CNS relapse of precursor B-cell acute lymphoblastic leukemia occurring 4 years after initial diagnosis.

The blast exhibit an unusual hypergranular cytomorphology with obscuration of cytoplasm by prominent azurophilic granules. These features make this particular blast morphology reminiscent of both promyelocytes and basophils, though cytochemistry for myeloperoxidase (performed at initial diagnosis) was negative. Sometime, these blasts exhibit positivity for Sudan Black B, a cytochemical markers for myeloid granules, but this does not connote myeloid differentiation in such cases.

Flow cytometry at diagnosis identified typical precursor B-cell (“common") immunophenotype (CD19 +, CD10 +, TdT +) with partial CD20 and evidence of isolated trisomy 21 and gain of RUNX1 by cytogenetics.

ALL blasts with granules have sometimes been associated with:

• presence of the Philadelphia chromosome

  ALLs that occur in Down syndrome.