The classification system for this type of cancer aims to help define, diagnose, and treat the disease and improve outcomes.
Myelodysplastic syndromes (MDSs), which are now also called myelodysplastic neoplasms, are a group of rare cancers that affect blood-producing cells in your blood marrow. They lead to the overproduction of abnormal, immature blood cells that overcrowd healthy red blood cells, white blood cells, or platelets.
MDSs sometimes develop into acute myeloid leukemia (AML). They used to be known as pre-leukemia, but this term isn’t frequently used anymore because many cases don’t transform into leukemia.
In 2022, the
Understanding which type you have can help you and your doctor predict how quickly your MDS will progress and decide on the best treatment options.
Here’s what to know.
MDSs are classified based on how your blood and bone marrow cells look under a microscope and whether there are genetic changes to these cells. When classifying MDSs, doctors consider factors such as:
- your white blood cell, red blood cell, and platelet counts
- the percentage of your blood cells that look abnormal under a microscope
- certain changes to the chromosomes in your bone marrow cells
- the portion of cells in your blood and bone marrow that are abnormal and immature
- the presence and proportion of abnormal red blood cell precursors called ring sideroblasts
The 2022 guidelines from the WHO break down several types of MDSs into two main categories: genetic and morphological.
Genetic MDS types
There are now three main types of MDS categorized by their definitive genetic abnormalities.
MDS with low blasts and isolated 5q deletion (MDS-5q)
In people with MDS-5q, cells in the bone marrow are missing part of chromosome 5. Cells may also show other genetic abnormalities, not including a partial or full loss of chromosome 7.
Other characteristics of MDS-5q include:
- a low number of one or two types of blood cells, with red blood cells most commonly affected
- an elevated number of at least one type of abnormal blood cell
According to the
MDS with low blasts and SF3B1 mutation (MDS-SF3B1)
This is a newer MDS categorization from the WHO. It takes the place of one that was called MDS with ring sideroblasts (MDS-RS).
MDS-SF3B1 involves a low percentage of ring sideroblasts (immature red blood cells that contain extra iron around their nucleus) and a mutation on the SF3B1 gene. MDS-SF3B1 is thought to include more than
MDS with biallelic TP53 inactivation (MDS-biTP53)
This new subtype of MDS involves mutations that lead to an inactivated TP53 gene, which is responsible for making a protein that regulates cell division.
When this occurs, it’s now known as MDS-biTP53.
Morphological MDS types
Three types of MDS are now morphologically defined, which means they’re defined based on the structure of the cells involved.
Hypoplastic MDS (MDS-h)
MDS-h is a newly defined, distinct disease type. It’s associated with an attack on certain cells responsible for bone marrow renewal, as well as an overproduction of inflammatory cytokines. As a result, the bone marrow contains fewer cells than it usually would.
Many features of MDS-h can overlap with those of other conditions, such as paroxysmal nocturnal hemoglobinuria and aplastic anemia, so careful morphologic evaluation is necessary for a proper diagnosis.
MDS with low blasts (MDS-LB)
This type of MDS is marked by an unusually low number of ring sideroblasts in the bone marrow and bloodstream.
MDS with increased blasts (MDS-IB)
This type of MDS is defined by a higher number of ring sideroblasts in the bone marrow and blood, along with a lower number of at least one type of blood cell. This type of MDS may be broken down into one of three categories based on additional diagnostic criteria:
- MDS with fibrosis (MDS-f)
MDSs are classified as primary MDSs when there’s no obvious cause, which is more common. If doctors suspect a specific cause, they refer to the disease as secondary MDS.
According to the
- prior treatment with chemotherapy (treatment-related MDS)
- exposure to high doses of radiation, as in people who
survive atomic bomb explosionsor nuclear reactor accidents
- long-term exposure to benzene and other chemicals
The Revised International Prognostic Scoring System (IPSS-R) is a commonly used diagnostic tool for MDS. It helps doctors predict a person’s overall survival and the risk of MDS transforming to AML.
This scoring system projects a score of 1–5 based on the following:
- any genetic changes that are present
- the number of blasts in the bone marrow
- the degree of cytopenias
The IPSS-R also plays a role in determining treatment options for MDS.
A newer scoring system has been created based on the molecular characteristics of MDS. However, more research is needed to find out how clinically useful this system is before it can be implemented for regular use.
Each person’s situation is different based on overall health, age, MDS subtype, and response to treatment. It’s always best to discuss your individual outlook with your doctor or oncology team.
MDSs are a group of blood cancers involving overproduction of abnormal, immature blood cells and a low count of healthy blood cells. MDS subtypes are defined based on how your blood and bone marrow cells look under a microscope and whether any genetic changes are present.
Understanding which type of MDS you have can help your doctor predict the long-term progression and outlook for your condition.