Discussion
In this case report, the patient was diagnosed with BPDCN arising from
MDS/MPN-RS-T that progressed into clinical TLS immediately after the
initiation of chemotherapy. Majority of patients with MDS/MPN-RS-T have
a SF3B1 mutation [7]. Although SF3B1 mutations were
not examined in this case, morphologically apparent dysplasia and the
presence of ringed sideroblasts strongly supported the diagnosis of
MDS/MPN-RS-T. On the other hand, while there is one case report about a
patient with MDS/MPN-RS-T that was positive for both CALR andSF3B1 gene mutations [8], BPDCN with CALR mutation has
not yet been reported to the best of our knowledge. Therefore, in this
case, MDS/MPN-RS-T might already have been accompanied with CALRmutation.
TdT negativity was reportedly associated with inferior survival in BPDCN
[9]; however, whether the aggressive clinical course observed in
this case was typical for TdT-negative BPDCN remains unknown.
Conversely, majority of patients with BPDCN expressing cMyc were
reportedly accompanied by 8q24 rearrangement, immunoblastoid morphology,
and skin lesions [10]. Although 8q24 rearrangement was not examined
in this case, the patient had no skin lesions and his blasts showed
classic cytomorphology, which suggested that his clinical features were
not typical for MYC-positive BPDCN.
Previous studies showed that BPDCN with leukemic presentation without
skin manifestation rarely occurs and tends to present with cytopenia
rather than leukocytosis [11]. However, although the patient had
leukemia at diagnosis, it was not accompanied with skin lesions and
showed very high WBC count, suggesting it to be a very rare case.
Moreover, rapid increase in WBC counts and massive splenomegaly
indicated a very high tumor burden and rapid tumor growth. The SMILE
regimen was selected because it was effective for ANKL [12] and the
etoposide contained in SMILE regimen was also effective for BPDCN
[13]. Although occurrence of TLS was cautiously considered in spite
of low Ki67 index and enough hydration and febuxostat were provided to
the patient for the prevention of TLS, he developed fatal TLS. More
rigorous management including the early use of rasburicase and induction
of hemodialysis is required.
Although the risk prediction of TLS in BPDCN is difficult because of the
rarity and heterogeneity of this disease, the evaluation of peripheral
blood WBC counts and serum LDH concentration may be useful for risk
classification of TLS in BPDCN as in acute leukemia [14].
In conclusion, BPDCN shows clinically heterogeneous characteristics, and
patients with clinical symptoms suggesting an aggressive clinical course
with high tumor burden, including high WBC count or splenomegaly, should
be carefully considered to prevent TLS.
Financial disclosure statement: The authors have nothing to
disclose.
Conflict of Interest: There are no conflicts of interest to
report.
Author Contribution: KS selected the patient and designed the
manuscript. KS, MI, NF, and AK wrote the manuscript. RF performed the
immunohistochemistry. All the authors reviewed the paper and agreed with
the final version.