In oncology, these terms describe the number of chromosomes found within a cancer cell compared to the normal human count of 46.
- Hyperdiploidy refers to an abnormally high number of chromosomes. In adult Acute Lymphoblastic Leukemia (ALL), this is specifically defined as having 51–65 chromosomes. It is generally considered a good-risk or standard-risk feature.
- Hypodiploidy refers to an abnormally low number of chromosomes. In adult ALL, this is defined as having fewer than 44 chromosomes. It is a poor-risk feature associated with a more aggressive disease course and inadequate long-term prognosis.
In other myeloid malignancies like AML or MDS, these are often grouped under “complex karyotypes” (having three or more chromosomal abnormalities), which is almost always an unfavorable prognostic factor.
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