骨髄異形成症候群myelodysplastic syndrome, MDSにおける異形成とは何か。

まとめ:MDSにおける異形成とは、
1 Dyserythropoesis
赤血球(赤芽球)の異形成
2 Dysgranulopoiesis
白血球(顆粒球系)の異形成
3 Dysmegalocytopoiesis
巨核球系の異形成
の三系統の造血細胞の異常を言う。

復習:
骨髄造血細胞の正常分化:九州大学:pdf.
これら正常分化を理解すれば、下記の異形成がどのように異常かが理解しやすい。


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骨髄異形成症候群における異形成とは何か。

WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, Fourth Edition:こちら

Morphologic manifestations of dyplasia (p92)
参考文献:Pathobiology. 2007;74(2):97-114.
Histopathology in the diagnosis and classification of acute myeloid leukemia, myelodysplastic syndromes, and myelodysplastic/myeloproliferative diseases.
Orazi A. こちら.
こちら。pdf

1 Dyserythropoesis
赤血球(赤芽球)の異形成
2 Dysgranulopoiesis
白血球(顆粒球系)の異形成
3 Dysmegalocytopoiesis
巨核球系の異形成
の三系統の造血細胞の異常を言う。

1 Dyserythropoesis
核の異常
Nuclear budding
Internuclear bridging
Keryorrhexis
Multinuclearity
Nuclear hyperloblation
Megaloblastic changes
細胞質の異常
Ring sideroblasts
Vacuolization
PAS染色陽性

2 Dysgranulopoiesis
Small or unusal large size
Nuclear hypoloblation
(偽Pelger-Huet核異常)
Irregular hypersegmentation
Decreased granules; agranularity
偽Chediak-Higashi顆粒
Auer小体

3 Dysmegalocytopoiesis
Micromegakaryocyte
Nuclear hypoloblation
Multinucleation (normal megakaryocytes are uninucleate with lobulated nuclei)

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ベックマンの情報:こちら。

顆粒球系の異形成  dysgranulopoiesis:こちら
顆粒球は低顆粒や偽ペルゲルの核異常が異形成のポイントが高い。

赤芽球の異形成:こちら
赤芽球系の巨赤芽球様変化は、幼若型での判定は困難なため、成熟型で核の遅延現象を掴む. しかし赤芽球の異形成はMDSに特異的でないとされている. またPAS陽性はMDSの診断に有効です.

赤芽球系の異形成 (骨髄のFe染色所見から):こちら
赤芽球は環状鉄芽球の増加に異形成のポイントが高い.

巨核球系の異形成 dysmegakaryopoiesis:こちら
巨核球は、小型巨核球に異形成のポイントが高い. 単円核や多分離核のものは頻度が高い場合をもって有効とされている.

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Myelodysplastic syndromes. Am J Clin Pathol. 2009 Aug;132(2):290-305. doi: 10.1309/AJCPRCXX4R0YHKWV.
Orazi A.
こちらpdf.

芽球とは
Blasts
The enumeration of blasts is important for the diagnosis
and classification of MDSs, and, in most studies, the blast percentage
is one of the most important prognostic indicators.1,2
It is also an integral component of currently used prognostic
scoring systems such as the International Prognostic Scoring
System11 and the more recent WHO classification–based
prognostic scoring system.19 Blasts should be carefully enumerated
from well-prepared peripheral blood smears and bone
marrow aspirate smears. Immature cells to be included in the
blast count include myeloblasts—without and with a few
fine azurophilic granules—monoblasts, and megakaryoblasts.
Promonocytes are also considered as “blast equivalents” in
the WHO classification scheme.1 These cells, which in the
absence of cytochemistry for esterase are morphologically
difficult to distinguish from promyelocytes and early myelocytes,
are rarely found in MDSs. Their presence suggests
a diagnosis of chronic myelomonocytic leukemia or, in the
presence of an increased blast count, AML with monocytic
differentiation.
The blast count derived from the aspirate smears should
be carefully correlated with the estimate from the biopsy sections.1,2,20-22
Often, in the marrow biopsy specimen, blasts may
be hard to appreciate, particularly if there is marrow fibrosis.
In such cases, an immunohistochemical stain for CD34 antigen
may be very helpful.22-26 However, because not all blasts
are CD34+, care must be taken not to use the CD34 result in
lieu of careful morphologic assessment. Additional markers
can be used to facilitate the visibility of CD34– blasts (eg,
CD117, lysozyme, CD68). Myeloperoxidase is often weak or
negative in blasts seen in MDSs. Flow cytometry may help in
assessing the frequency of marrow blasts and to confirm their
immunophenotype. In addition, aberrant antigen expression
and side scatter abnormalities (owing to low granularity in the
granulocytic cells) have also been shown to roughly correlate
with the severity of the MDS.