A great explanation of cytogenetics...

[Sally C]

Authored by Mausmish..

Cytogenetics from my personal experience:

I was extremely confused when I received my first cytogenetic report. I understood that I had "complex cytogenetics" meaning multiple chromosome abnormalities and that this was very bad news. After a lot of reading, this is my basic understanding of the notations in the report. Notations vary slightly from lab to lab. Anyone, please correct me if I'm wrong about any of this info. I have no medical expertise and don't want to give out misinformation.

Cytogenetics, for our purposes, is the study of chromosomes and their structure. We are not talking about inheritance and genetics. Each of our cells has 23 pairs of chromosomes or a total of 46. The term "karyotype" means the arrangement and structure of the chromosomes. If one has no chromosome abnormalities, it will be designated 46,XX for a female or 46,XY for a male.

The pairs of chromosomes are labeled 1 through 23, and each individual chromosome has two arms, the top or short arm is labeled "p" and and the bottom or long arm is labeled "q". Each arm has numerically labeled regions.

In damaged chromosomes, anomalies or defects are generally classified as deletions, additions, translocations or inversions.

Deletions:If an entire chromosome is missing, it is designated monosomy, such as "monosomy 7" or "-7"; If only part of a chromosome is missing it is designated del( ). For example a deletion of the entire q arm of chromosome 5 might be notated "del(5q)" or "-5q"; if only part of an arm is missing, there will be an additional notation showing which region, for example "del(5q21:33)" or "del(5)(q21)".

Additions: Sometimes there is an extra copy of a chromosome, called trisomy, such as "trisomy 8" or "tri(8)" or "+8". Sometimes instead of a copy, there is an addition of unknown origin, designated "marker" such as "mar(unknown)" or "+mar".

Inversions: Sometimes the arms of a chromosome are partially or completely inverted - all or part of the p arm is swapped with all or part of the q arm on the same chromosome. This is noted something like "inv(4)(p13q22)" to show which regions are swapped.

Translocations: Sometimes part of a chromosome gets swapped with or added to part of a different chromosome. This is noted something like "t(9;22)(q34;q11.2)" meaning part of chromosome 9 (region q34) is swapped with part of chromosome 22 (region q11.2).

Going back to my own report as a full example, here is what it showed:

46,XX,-3,del(5)(q14q33),-6,+8,+mar[14]/46,XX[6]

My sample size was 20 cells. Of these [14] were abnormal with multiple anomalies and [6] had no defects.

46,XX = each cell had 46 chromosomes, all female

-3 = monosomy 3 = one of the chromosomes in pair number 3 was completely missing

del(5)(q14q33) = region 14-33 of the long arm q of one of my chromosomes in pair number 5 was deleted. This is common in MDS. If it had been the only anomaly, my prognosis would have been good but combined with my other anomalies, it wasn't.

-6 = monosomy 6 = one of the chromosomes in pair number 6 was completely missing

+8 = trisomy 8 = I had an extra copy of one of the chromosomes in pair number 8. This may be associated with AML.

+mar = I had some extra chromosome material of unknown type and origin. Sometimes the material can be identified and offers clues to prognosis or origin. Mine did not.

After 3 cycles of Vidaza, I had the same abnormalities but only in 1 of the 20 cells sampled in my biopsy, so the report looked like this:
46,XX,-3,del(5)(q14q33),-6,+8,+mar[1]/46,XX[19]

I'm happy to say that I've had 4 bone marrow biopsies since November 2010, all with cytogenetics reported as 46,XX[20], i.e. no abnormalities.

[PattiDean]

Thank you Sally!

[Whizbang]

Here's my 'empty' tree...

Cytogenetic Diagnosis:
42,XY,der(2)t(2;5)(p21;p13),-5,-7,der(8)t(?7;8)(p15;p23)ins(8;15)(p2
3;q?26q?22),-15,der(17)
ins(17;?)(q11.1;?),-18,-20,+mar[8]/42,idem,-der(17),+der(17)del(17)(
p11.2)ins(17;?)(q11.1;?)[2].
ish
der(2)(D5S721,D5S23+),der(8)(PML+),der(17)1ns(17)(TP53+,D17Z1+,RARA+
),der(17)del (17)ins(17)(TP53-,D17Z1+,RARA+).nuc ish
5p15.2(D5S721,D5S23x2),5q31(EGR1x1)[52/200],
7p11.1-q11.1(D7Z1),7q31(D7S522x1)[69/200],17p13.1(TP53x1),17p11.1-
q11.1(D17Z1x2) [26/200],15q24(PMLx2)17q21(RARAx2)[200]

The hypodiploid complex karyotype seen in this study, in particular with del(5q), deletion or monosomy 7q, del(17p)/TP53, and monosomy 20, is consistent with myeloid disorder. The presence of multiple aberrations, including deletions of 7q and TP53, is indicative or evolution and are adverse prognostic indicators. Correlation with other clinical and laboratory findings and follow-up studies are recommended to monitor patient status.