Inversion of chromosome 16 is associated with acute myeloid leukemia with abnormal eosinophils
These abnormal eosinophils have mixed eosinophilic and basophilic granules
How is the cytogenetic abnormality determined diagnostically?
A brief introduction to cytogenetics…
Cytogenetics is the microscopic investigation of the DNA structure/content at the chromosomal level using banding of metaphase preparations
Banding = darker and lighter areas on a chromosome, which are reproducible across specimens
Most common type of banding is G-banding:
- Dark bands: AT-rich, heterochromatic, fewer active genes
- Light bands: CG-rich, euchromatic, more active genes
From Wikipedia ⬇️
Our talented technologists identify banded chromosomes by assessing (in order):
- Chromosome size
- Centromere position
- Banding pattern
From ASH and Wikipedia ⬇️
Cytogenetics studies are essential in making a diagnosis of AML with inv 16
This can be subtle on conventional karyotype, so further testing with FISH/molecular is warranted if the karyotype is normal but the morphology suggests inv 16
From PEIR @UABPathology ⬇️
The inversion of chromosome 16 (or the translocation t(16;16) leads to the fusion of CBF-beta and MYH11.
CBF normally binds to enhancers/promoters of genes involved in hematopoiesis, increasing transcription of these target genes, leading to hematopoietic differentiation/maturation
With the fusion gene, this process is blocked ➡️ less transcription of target genes ➡️ less hematopoietic differentiation/maturation ➡️ disease
Finally, it's important to note that AML with inversion 16 is considered to be in the favorable risk category
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