RT Book, Section
A1 Lichtman, Marshall A.
A1 Kaushansky, Kenneth
A1 Kipps, Thomas J.
A1 Prchal, Josef T.
A1 Levi, Marcel M.
SR Print(0)
ID 1126652579
T1 Myelodysplastic Syndromes (Clonal Cytopenias and Oligoblastic Myelogenous Leukemia)
T2 Williams Manual of Hematology, 8e
YR 2011
FD 2011
PB McGraw-Hill Education
PP New York, NY
SN 9780071622424
LK hemonc.mhmedical.com/content.aspx?aid=1126652579
RD 2024/04/19
AB Myelodysplasia  is  the  term  used,  as  a  generalization,  to  encompass  a  diverse  group  of  myeloid  neoplasms  that  have  in  common  (a)  their  origin  in  a  somatically  mutated  multipotential  hematopoietic  cell,  (b)  ineffective  hematopoiesis  (late  precursor  apoptosis)  leading  to  cytopenias  despite  a  normocellular  or  hypercellular  marrow,  and  (c)  a  propensity  to  undergo  clonal  progression  to  acute  myelogenous  leukemia  (AML).Spectrum  ranges  from  (a)  indolent  disorder  with  mild  or  moderate  anemia  to  (b)  more  troublesome  multicytopenias  without  morphologic  evidence  of  leukemic  cells  to  (c)  oligoblastic  (subacute)  myelogenous  leukemia  with  leukemic  blast  cells  in  the  marrow  and  blood  (Table  42–1).Clonal  cytopenia  refers  to  disorders  without  increased  leukemic  blast  cells  in  the  marrow.  The  manifestations  vary  from  isolated  anemia  with  a  nearly  normal  marrow  to  severe  multicytopenias  with  hypercellular  marrow  and  with  dysmorphia  of  marrow  precursors  and  blood  cells.Oligoblastic  or  subacute  myelogenous  leukemia  (synonym:  refractory  anemia  with  excess  blasts)  refers  to  patients  with  cytopenias  and  with  marrow  containing  2  to  19  percent  leukemic  blast  cells.  (The  World  Health  Organization  [WHO]  uses  the  range  5  to  19%.)If  the  marrow  blast  cell  count  is  20  percent  or  higher,  the  disease  is  considered  acute  myelogenous  leukemia  and  so  treated.The  use  of  <5  percent  marrow  blasts  as  a  demarcation  is  an  anachronism  dating  from  a  decision  made  in  1955,  at  which  time  the  first  definition  of  remission  in  childhood  acute  lymphoblastic  leukemia  used  <5  percent  marrow  blasts  (and  other  salutary  changes)  to  avoid  additional  cytotoxic  treatment  in  an  era  without  platelet  transfusion,  potent  wide-spectrum  antibiotics,  or  other  support  for  children  treated  with  multidrug  regimens.  Also,  only  light  microscopy  was  available  to  distinguish  nonleukemic  lymphocytes  in  treated  marrows  from  residual  leukemic  lymphoblasts.  This,  so-called,  "5  percent  rule"  is  irrelevant  at  the  time  of  diagnosis,  especially  in  the  case  of  myeloblasts,  but  it  has  been  ensconced.The  use  of  19  versus  20  percent  blasts  to  distinguish  oligoblastic  myelogenous  leukemia  (refractory  anemia  with  excess  blasts)  from  AML  is,  of  course,  arbitrary  and  without  pathobiologic  foundation.  The  physician  should  determine  management  of  the  case  by  several  factors  (e.g.,  physiologic  age,  severity  of  cytopenias,  transfusion  requirements,  frequency  and  severity  of  infections)  not  principally  whether  a  patient  with  myelogenous  leukemia  has  15,  20,  or  25  percent  blast  cells.