TY  - CHAP
M1  - Book, Section
TI  - Myelodysplastic Syndromes (Clonal Cytopenias and Oligoblastic Myelogenous Leukemia)
A1  - Lichtman, Marshall A.
A1  - Kaushansky, Kenneth
A1  - Prchal, Josef T.
A1  - Levi, Marcel M.
A1  - Burns, Linda J.
A1  - Armitage, James O.
PY  - 2017
T2  - Williams Manual of Hematology, 9e
AB  - Myelodysplasia  or  myelodysplastic  syndrome  (MDS)  is  the  term  used,  as  a  generalization,  to  encompass  a  diverse  group  of  myeloid  neoplasms  that  have  in  common  (1)  their  origin  in  a  somatically  mutated  multipotential  hematopoietic  cell,  (2)  ineffective  hematopoiesis  (late  precursor  apoptosis)  leading  to  cytopenias  despite  a  normocellular  or  hypercellular  marrow,  and  (3)  a  propensity  to  undergo  clonal  progression  to  acute  myelogenous  leukemia  (AML).The  spectrum  ranges  from  (1)  indolent  disorder  with  mild  or  moderate  anemia  to  (2)  more  troublesome  multicytopenias  without  morphologic  evidence  of  leukemic  cells  to  (3)  oligoblastic  (subacute)  myelogenous  leukemia  with  leukemic  blast  cells  in  the  marrow  and  blood.Clonal  cytopenia  refers  to  disorders  without  increased  leukemic  blast  cells  in  the  marrow  or  blood.  The  manifestations  vary  from  isolated  cytopenia  (eg,  anemia)  with  a  marrow  with  erythroid  dysmorphia  to  severe  multicytopenias  with  hypercellular  marrow  and  with  dysmorphia  of  marrow  precursors  in  each  major  lineage  and  of  blood  neutrophils,  red  cells,  and  platelets.Because  the  neoplasm  originates  in  a  multipotential  hematopoietic  cell  (eg,  the  lymphohematopoietic  stem  cell),  careful  inspection  of  blood  and  marrow  will  usually  identify  mild  involvement  of  all  three  major  lineages  (eg,  low  normal  blood  cell  counts)  or  subtle  morphological  abnormalities.Oligoblastic  or  subacute  myelogenous  leukemia  (synonym:  refractory  anemia  with  excess  blasts)  refers  to  patients  with  cytopenias  and  with  marrow  containing  3%  to  19%  leukemic  blast  cells.  (The  World  Health  Organization  [WHO]  currently  uses  the  range  of  5%  to  19%  blast  cells.)If  the  marrow  blast  cell  count  is  20%  or  higher,  the  disease  is  considered  AML  and  so  treated.The  use  of  less  than  5%  marrow  blasts  as  a  demarcation  between  a  normal  and  pathological  blast  percentage  is  an  anachronism  dating  from  a  decision  made  in  1955,  at  which  time  the  first  definition  of  a  remission  in  childhood  acute  lymphoblastic  leukemia  used  less  than  5%  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,”  however,  is  not  relevant  at  the  time  of  diagnosis,  especially  in  the  case  of  myeloid  neoplasms,  has  not  been  validated,  but  it  has  been  ensconced.The  use  of  less  than  or  greater  than  or  equal  to  20%  blasts  to  distinguish  oligoblastic  myelogenous  leukemia  (refractory  anemia  with  excess  blasts)  from  AML  is  arbitrary  and  without  pathobiologic  foundation.  Studies  have  shown  no  difference  in  phenotypic  manifestations  or  survival  between  populations  with  10%  to  19%  as  compared  to  20%  to  30%  leukemic  myeloblasts.  The  physician  should  determine  management  of  the  case  by  several  factors  (eg,  physiologic  age,  severity  of  cytopenias,  cytogenetic  or  oncogene  risk  category,  transfusion  requirements,  frequency  and  severity  of  infections),  not  principally  whether  a  patient  with  myelogenous  leukemia  has  10%,  15%,  20%,  or  25%  blast  cells.More  rarefied  diagnostic  categories  are  in  the  WHO  classification  shown  in  Table  44–1  and  are  currently  being  revised.  These  categories  are  useful  in  ensuring  comparable  populations  in  therapeutic  or  prognostic  clinical  trails.  In  individual  patients,  management  ...
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/20
UR  - hemonc.mhmedical.com/content.aspx?aid=1133364083
ER  -