Case History
A two-and-a-half-year-old female child presented with fever and pallor
of 1-week duration. Examination revealed hepatomegaly (span 11 cm) and
splenomegaly (2 cm below the left subcostal margin). The hemoglobin was
46 g/L, platelet count 14.0 x109 /L and total
leucocyte count 14.7 x 109/L. Peripheral blood film
showed 62% circulating blasts (Fig. 1A-B ). Bone marrow
aspiration revealed 82% blasts with scanty, agranular basophilic
cytoplasm without Auer rods; 2% of the blasts showed cytochemical
myeloperoxidase positivity. On flow cytometry, the blasts expressed
bright CD19 and dim CD10 along with cytoplasmic CD79a and CD22. There
was cross-lineage antigen expression of CD33 (bright; 90% cells) and
CD13 (dim; 14% cells). The blasts were also positive for CD34, HLA-DR,
CD38, CD81 and CD86; and were negative for CD20, CD117, T-lineage
associated markers, monocytic & megakaryocytic-lineage associated
markers. Cytoplasmic myeloperoxidase (anti-MPO) expression was also not
noted. A working diagnosis of BCP-ALL with aberrant CD33 expression was
rendered, following which the child was initiated on the Standard Risk
(SR) BCP-ALL protocol of the Indian Childhood Collaborative Leukemia
Group (ICiCLe), comprising of a pre-phase of prednisolone 60
mg/m2/d in three divided doses. 4
Fluorescent in-situ hybridization (FISH) testing with dual-colour
dual-fusion probes for BCR-ABL1 and ETV6-RUNX1, dual
break-apart probes for KMT2A and TCF3 (CytoTest Inc.
Rockville, United States) revealed presence of TCF3 translocation
in more than 80% of cells (Fig. 1E) . Subsequently, bothTCF3-PBX1 and TCF3-HLF translocations were excluded using
a tri-colour probe (Cytocell Ltd, Cambridge).
After one week of pre-phase steroid therapy, although the toddler
clinically appeared well, her leukocyte count increased to
63x109/L with 60% circulating blasts. On peripheral
blood smear examination, in contrast to the morphology at diagnosis,
these blasts were larger with indented nuclei, prominent nucleoli and
moderate amount of granular basophilic cytoplasm without Auer rods. The
blasts showed unequivocal cytochemical myeloperoxidase positivity in
20% of the cells (Fig. 1C-D ). The smaller lymphoblasts noted
at the time of diagnosis were absent. Repeat flow cytometry performed on
peripheral blood showed that 90% of the blasts expressed myeloid
antigens (CD13, CD33, CD64, CD14, CD36, CD15 and cytoplasmic
myeloperoxidase. The remaining 10% blasts showed the initial
immunophenotype of BCP-ALL. The initial cytochemical myeloperoxidase and
anti-MPO (flow cytometry) results were reviewed and the negative report
(<3% positivity) was reverified.
Repeat FISH testing revealed the TCF3 rearrangement in blasts as
well as granulocytes (Fig. 1F) . In view of absence of
metaphase, further FISH testing was performed using a commercially
available dual-colour break-apart probe (ZytoVision GmbH, Germany) that
confirmed rearrangement of ZNF384 (Fig. 1G) . The
diagnosis was revised to TCF3-ZNF384 [t(12;19)(p13;p13)]
rearranged MPAL, B/myeloid. The patient’s risk stratification was
upgraded to High-Risk (HR) and appropriate management
initiated4.
Her remaining induction phase chemotherapy was interrupted by two
episodes of febrile neutropenia, both managed with antimicrobials.
End-of-induction bone marrow revealed 03% blasts and no measurable
residual disease (MRD) on high-resolution multiparameter flow cytometry.
She had a stormy course prior to consolidation too, developing a fungal
brain abscess requiring surgical drainage, leading to a 2-week delay in
start of consolidation therapy. Currently, the patient is on an
augmented BFM (Berlin-Frankfurt-Munster) consolidation protocol and
continues her antifungal prophylaxis.