Myelodysplastic syndrome, unclassifiable

ICD-O-2 Morphology

ICD-O-3 Morphology

9989/3: Myelodysplastic syndrome, unclassifiable
Effective 2001 and later


for cases diagnosed 2001 and later

Primary Site(s)

Primary site must be bone marrow (C421)

Abstractor Notes

Myelodysplastic syndrome, NOS is a generic disease description. DCO cases or path report only cases may stay in this classification. In most cases, NOS histology is only the provisional diagnosis; the physician will run further diagnostic procedures and look for various clinical presentations to identify a more specific disease.

Further review of the medical record should be done to look for the tests listed as definitive diagnosis.The more specific
myelodysplastic syndromes are:

1. Myelodysplastic syndrome with excess blasts (9983/3)
2. Myelodysplastic syndrome with multilineage dysplasia (9985/3)
3. Myelodysplastic syndrome with ring sideroblasts and single lineage dysplasia (9982/3)
4. Myelodysplastic syndrome with single lineage dysplasia (9980/3)
5. Refractory cytopenia of childhood (9985/3)
6. Refractory neutropenia (9991/3)
7. Refractory thrombocytopenia (9992/3)
8. Myelodysplastic syndrome with ring sideroblasts and multilineage dysplasia (9993/3)

If the characteristics of a specific subtype of MDS develops later in the course of the disease, change the histology code to the more specific diagnosis.
The peripheral blood and bone marrow are the principal sites of involvement.

About 10% of MDS patients have bone marrow that is hypocellular. These cases are referred to as hypoplastic MDS. When considering the diagnosis of hypoplastic MDS, it is important to exclude toxic myelopathy and auto-immune disorders.

This is a clinical diagnosis. When the testing has excluded other diseases, the physician uses the information from the equivocal test results plus the patient's clinical history to make a diagnosis of myelodysplastic syndrome.

The patient receives supportive care. Red blood cells are transfused for anemia.

Hematologic Transplant and/or Endocrine Procedures treatments include bone marrow and stem cell transplants.

Diagnostic Confirmation

This is a histology for which the Definitive Diagnostic Method does not include Genetics Data or Immunophenotyping, thus Diagnostic Confirmation should never be 3. If genetics and/or immunophenotyping are available, re-review to see if a more specific neoplasm can be coded.


Not Applicable

Module Rule


Alternate Names

Hypoplastic myelodysplastic syndrome (MDS)
MDS, unclassified
Myelodysplastic disorder
Myelodysplastic syndrome, NOS
Preleukemia [OBS]
Preleukemic syndrome [OBS]
Smoldering leukemia


Blood: Cytopenias, no blasts
Bone marrow: <5% blasts, dysplasia in granulocytes or megakaryocytes

The myelodysplastic syndromes (MDS, formerly known as "preleukemia") are a diverse collection of hematological conditions united by ineffective production of blood cells and varying risks of transformation to acute myelogenous leukemia (AML). Anemia requiring chronic blood transfusion is frequently present.

Definitive Diagnostic Methods

Bone marrow biopsy
Clinical diagnosis

Genetics Data





Hematologic Transplant and/or Endocrine Procedures

Transformations from


Corresponding ICD-9 Codes

238.75 Myelodysplastic syndrome, unspecified

Corresponding ICD-10 Codes

D46.9 Myelodysplastic syndrome, unspecified

Corresponding ICD-10-CM Codes (U.S. only)

D46.9 Myelodysplastic syndrome, unspecified (effective October 01, 2015)
D46.Z Other myelodysplastic syndrome, unspecified (effective October 01, 2015)

Signs and Symptoms

Easy bruising or bleeding
Petechiae (flat, pinpoint spots under the skin caused by bleeding
Shortness of breath
Skin paler than usual
Weakness or feeling tired

Diagnostic Exams

Blood chemistry studies
Cytogenetic analysis
FISH (flourescence in situ hybridzation)
Flow cytometry
Peripheral blood smear

Progression and Transformation


Epidemiology and Mortality



Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition)
IARC: Lyon 2017
Section: Myelodysplastic syndromes
Pages: 116

International Classification of Diseases for Oncology, Third Edition, Second Revision. Geneva: World Health Organization, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes

National Cancer Institute
Section: General Information About Myelodysplastic Syndromes