New WHO classification of malignant hematological diseases
May 8, 2002 (abbreviated version)
A new classification system has been worked out for malignant hematological
conditions by the WHO. The part which concerns the myeloid malignant diseases
only recently started to appear in the literature. The majority of the
textbooks available discusses only the old FAB classification system.
The differences of the old and new classification systems are summarized
below.
Contents
General remarks
The new WHO classification will be published in book form in the
series "International Histological Classification of Tumors"
titled "WHO classification of neoplastic diseases of hematopoietic
and lymphoid tissues".(It was quoted as "in press" in 1999,
but it has now come out yet, as far as I know.) The classification
is discussed in a 1999 issue of the Journal of Clinical Oncology
(Vol 17, No 12, December, pp 3835-3849). The
online abstract
is available. A paper copy can be borrowed at the 17th floor in the
Institute of Pathophysiology. This paper is mainly useful for teachers,
but students may borrow it as well, if they feel they need it.
Classification of myeloid malignancies
FAB |
Chronic myeloproliferative diseases |
|
Myelodysplastic syndromes |
Acute myeloid leukamias |
|
WHO |
Chronic myeloproliferative diseases |
Myelodysplastic/myeloproliferative diseases |
Myelodysplastic syndromes |
Acute myeloid leukemias |
|
The WHO classification system puts a few diseases that show characteristics
of both myeloproliferative and myelodysplastic conditions into a new, separate
group (myeloproliferative/myelodysplastic diseases).
Chronic myeloproliferative diseases (MPD)
Malignant stem cell disorder of clonal origin with a chronic course.
It is characterized by splenomegaly and a high cell count in one or more
cell lines. The marrow is hypercellular with signs of differentiation,
there is no dysplasia.
Classification of chronic myeloproliferative diseases |
FAB |
Chronic myelogenous leukemia (CML) |
|
Agnogenic myeloid metaplasia with myelofibrosis (MF)
(Idiopathic myelofibrosis)
|
Polycythemia vera (EV) |
Essential thrombocytemia (ET) |
|
WHO |
CML Ph+: t(9;22)(qq34;q11), BCR/ABL |
Chronic neutrophilic leukemia |
Chronic eosinophilic leukemia/hypereosinophilic syndrome |
Chronic idiopathic myelofibrosis |
Polycythemia vera |
Essential thrombocytemia |
|
CML
The most important change is, that only the Ph+ cases are called
CML by the WHO. The Ph- cases (which show myelodysplastic signs, and
are known to have significantly worse prognosis) are called aCML
(atypical CML), and belong to the newly created
myelodysplastic/myeloproliferative group. The aCML term is somewhat
misleading, because it is not CML at all, but it was kept, having
no better alternative.
Myelodysplastic/myeloproliferative diseases
WHO: myelodysplastic/myeloproliferative diseases |
Atypical myelogenous leukemia (aCML) |
Chronic myelomonocytic leukemia (CMML) |
Juvenile myelomonocytic leukemia (JMML) |
CMML belonged to the MDS in the FAB classification. About one half
of the cases show proliferative, the other dysplastic signs, but
it looks like these are just different forms of the same disease.
Myelodysplastic syndromes (MDS)
Myelodysplastic syndromes |
FAB classification of MDS |
Refractory anemia (RA) |
Refractory anemia with ringed sideroblasts (RARS) |
Refractory anemia with excess blasts (RAEB) |
Refractory anemia with excess blasts in transformation (RAEB-T) |
Chronic myelomonocytic leukemia (CMML) |
|
WHO classification of MDS |
Refractory anemia |
| with ringed sideroblasts (FAB: RARS) |
| without ringed sideroblasts (FAB: RA) |
Refractory cytopenia with multilineage dysplasia (new) |
Refractory anemia with excess blasts (FAB: RAEB) |
5q- syndrome (new) |
unclassifiable (new) |
|
Major changes: the RAEB-T of the FAB is now
considered to be acute leukemia, not an MDS type.
CMML of the FAB was put into the new MPD/MDS group
by the WHO.
A new group was formed from those cases previously classified as RA or RARS
where the dysplasia affected more than one cell line, because the prognosis
has been found worse for these cases
(refractory cytopenia with multilineage dysplasia).
A new subgroup is 5q- syndrome (the loss of the long
arm of chromosome 5).
Acute myeloid leukemias (AML)
AML classification |
FAB |
M0: minimally differentiated |
M1: myeloblastic leukemia without maturation |
M2: myeloblastic leukemia with maturation |
M3: hypergranular promyelocytic leukemia |
M4: myelomonocytic leukemia |
M4Eo: variant, increase in marrow eosinophils |
M5: monocytic leukemia |
M6: erythroleukemia (DiGuglielmo's disease) |
M7: megakaryoblastic leukemia |
|
WHO |
AML with recurrent cytogenetic translocations |
| AML with t(8;21)(q22;q22) AML1/CBFalpha/ETO |
| Acute promyelocytic leukemia:
AML with t(15;17)(q22;q12) and variants PML/RARalpha |
| AML with abnormal bone marrow eosinophils inv(16)(p13;q22) vagy t(16;16)(p13;q22) CBFbeta/MYH1 |
| AML with 11q23 MLL abnormalities |
AML with multilineage dysplasia |
| With prior MDS |
| Without prior MDS |
AML with myelodysplastic syndrome, therapy related |
| Alkylating agent related |
| Epipodophyllotoxin related |
| Other types |
AML not otherwise categorized |
| AML minimally differentiated |
| AML without maturation |
| AML with maturation |
| Acute myelomonocytic leukemia |
| Acute monocytic leukemia |
| Acute erythroid leukemia |
| Acute megakaryocytic leukemia |
| Acute basophilic leukemia |
| Acute panmyelosis with myelofibrosis |
|
The changes are easily summarized: the leukemias with consistent
cytogenetic abnormalitites and those that are MDS related were
taken into separate groups, the rest of the old FAB classification was put
under the "AML not otherwise categorized" entry.
"REAL" classification of lymphoid malignancies
WHO classification of lymphoid malignancies (part 1: non-Hodgkin types) |
B cell |
Precursor B cell neoplasm |
| Precursor B lymphoblastic leukemia/lymphoma
(precursor B cell acute lymphoblastic leukemia) |
Mature (peripheral) B cell neoplasms |
| B cell chronic lymphocytic leukemia/small lymphocytic lymphoma |
| B cell prolymphocytic leukemia |
| Lymphoplasmacytic lymphoma |
| Splenic marginal zone B cell lymphoma (± villous lymphocytes) |
| Hairy cell leukemia |
| Plasma cell myeloma/plasmacytoma |
| Extranodal marginal zone B cell lymphoma of MALT type |
| Mantle cell lymphoma |
| Follicular lymphoma |
| Nodal marginal zone B cell lymphoma (± monocytoid B cells) |
| Diffuse large B cell lymphoma |
| Burkitt's lymphoma/Burkitt cell leukemia |
| |
|
T cell |
Precursor T cell neoplasm |
| Precursor T lymphoblastic lymphoma/leukemia
(precursor T cell acute lymphoblastic leukemia) |
Mature (peripheral) T cell neoplasms |
| T cell prolymphocytic leukemia |
| T cell granular lymphocytic leukemia |
| Aggressive NK cell leukemia |
| Adult T cell lymphoma/leukemia (HTLV-I+) |
| Extranodal NK/T cell lymphoma, nasal type |
| Enteropathy-type T cell lymphoma |
| Hepatosplenic T cell lymphoma |
| Subcutaneous panniculitis-like T cell lymphoma |
| Mycosis fungoides/Sézary syndrome |
| Anaplastic large cell lymphoma, primary cutaneous type |
| Peripheral T cell lymphoma, not otherwise specified (NOS) |
| Angioimmunoblastic T cell lymphoma |
| Anaplastic large cell lymphoma, primary systemic type |
|
WHO classification of lymphoid malignancies (part 2: Hodgkin disease) |
Nodular lymphocyte-predominant Hodgkin's disease |
Classical Hodgkin's disease |
| Nodular sclerosis Hodgkin's disease |
| Lymphocyte-rich classical Hodgkin's disease |
| Mixed-cellularity Hodgkin's disease |
| Lymphocyte-depletion Hodgkin's disease |
Tornoci Laszlo
Last modified: Wed May 8 22:57:10 CEST 2002