MLS 007 (Human Cytogenetics)

STUDENT ACTIVITY SHEET BS MEDICAL TECHNOLOGY / SECOND YEAR

Session # 13

Materials:
LESSON TITLE: NEOPLASIA NOMENCLATURE Book, pen and notebook, class list
LEARNING OUTCOMES:
References:
Upon completion of this lesson, the nursing student can:
1. Gersen, SL & Keagle, MB (2005). The Principles
1. Define the important terms in describing karyotypes of of Clinical Cytogenetics 2nd ed, Humana Press Inc.,
cancer New Jersey
2. Apply the rules in describing cancer karyotypes properly
3. Describe in details the karyotypes of cancer

SUBJECT ORIENTATION (10 minutes)

Students are asked to read the lesson ahead of time. The lesson is found in Section I, Chapter 3, pp 51-58 entitled
Neoplasia.

MAIN LESSON (50 minutes)

The basic rules for using the nomenclature apply when describing the karyotypes associated with cancer. However, special
situations, requiring additional guidelines, might arise in these cases. Therefore, special ISCN definitions and rules have
been devised for use with neoplasia.

Clones

A clone is defined as two cells that share the same abnormality or abnormalities, unless the change involves loss of
chromosome, in which case three such cells are required (because of the possibility of coincidental random chromosome
loss). During tumor progression, related subclones can evolve; related or unrelated clones are separated by slashes “/” and
the number of cells observed for each is given in square brackets “[ ]”.

Mainline, Stemline, Sideline, and Clonal Evolution

These terms can be confusing and are often misunderstood. The mainline (ml) is the term used to describe the most
common clone (i.e., the one represented by the most cells). This is a quantitative issue only. It does not necessarily indicate
the most basic clone in tumor progression, which is referred to as the stemline (sl). Clones that evolve from the stemline
are referred to as sidelines (sdl):

46,XY,t(9;22)(q34;q11.2)[5]/47,XY,+8,t(9;22)(q34;q11.2)[11]/46,XY,t(9;22)(q34;q11.2),i(17)(q10)[4]

Stemline mainline sideline

When more than one clone is present but no clear clonal progression is evident, the mainline is listed first, followed by each
clone in order of relative size. When clonal evolution is present, the stemline is listed first, with sidelines listed in order of
increasing complexity whenever possible, or by clone size when more than one sideline evolves independently from the
stemline, as in the preceding example.

Composite Karyotype (cp)

When a clone contains multiple abnormalities, a frequent occurrence is that not all changes are present in every cell, yet
the interpretation can be made that these cells do, in fact, represent a single abnormal clone rather than an evolving process.
To report such a phenomenon, the clone is described as a composite, using the abbreviation “cp” before the number in
brackets. It should be noted that this can occasionally produce seemingly contradictory data, as some cells will contain
additional copies of a chromosome that is missing in others.

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INTERPRETING A KARYOTYPE DESCRIPTION

Receiving a cytogenetic report that contains the description of a patient’s karyotype can create confusion, particularly if
complex rearrangements or multiple clones are present. Interpretation of the description of a karyotype can be facilitated
by breaking this description into its component parts. First, determine whether more than one cell line is present. This will
happen if constitutionally the patient is a mosaic or a chimera as is often the case with acquired cytogenetic abnormalities,
particularly in patients whose neoplasm is progressing. Because the first item described is always the number of
chromosomes present, each clone or cell line present will start with this number, and each is separated by a slash (/). Each
cell line can then be examined individually. If abnormalities present in the first clone listed are also present in another, the
description can be simplified by using the abbreviation “idem” to indicate this; note that idem is only used when a single
sideline is present. When more than one sideline is present, the abbreviations “sl” and “sdl” are used and each sideline is
numbered (sdl1, sdl2, etc.).

As discussed above, the sex chromosome complement follows the chromosome count. Sex chromosome abnormalities are
listed first, followed by autosomal abnormalities in numerical order. When abnormalities involve the same chromosome,
numerical changes are presented first, followed by structural abnormalities listed in alphabetical order, using the
abbreviations listed. Commas separate each abnormality listed, and so by examining the karyotype from comma to comma,
the abnormalities involved can be interpreted.

Consider the following example from a patient with AML:

47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

At first blush, receiving a report with this karyotype might be enough to scare away even the most confident clinician!
However, let us break this karyotype down into its component parts, which will simplify its interpretation. The slashes,
brackets, and listings of number of chromosomes tell us that three different clones are present:

47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]
/48,idem,+9,i(17)(q10)[12]
/46,XY[4]
Of the 20 cells examined, the first clone has 47 chromosomes and is represented by 4 cells. The second clone has 48
chromosomes; 12 of these cells were observed. Finally, four normal 46,XY cells are present. Now, let us look again at the
first cell line, the stemline in this case. It has an XY sex chromosome complement. It also has three cytogenetic
abnormalities: It has one chromosome 5 with an interstitial deletion of the material between bands q13 and q33 (on the long
arm):

47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

It has an extra copy of chromosome 8,

47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

and it has a translocation involving the long arms of chromosomes 9 and 22, at band q34 of chromosome 9 and band
q11.2 of chromosome 22:
47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

Yes, this is the “Philadelphia” rearrangement, which is sometimes also seen in patients with AML.

The second cell line contains the sex chromosomes and all of the abnormalities present in the first:
47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

plus an additional copy of chromosome 9:

47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

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and an isochromosome for the long arm of chromosome 17:
47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4].

Because this is the largest clone present (with 12 cells), it represents the mainline. Finally, as mentioned above, the third
cell line represents cells with a normal male karyotype:

47,XY,del(5)(q13q33),+8,t(9;22)(q34;q11.2)[4]/48,idem,+9,i(17)(q10)[12]/46,XY[4]

In the next example there are three cell lines; the stemline and two diverging sidelines.
46,XY,inv(16)(p13q22)[7]/47,sl,+22[8]/46,sdl1,–7[5]

The stemline consists of seven cells with an XX sex chromosome complement and an inverted chromosome16. The first
sideline consists of eight cells that also have an XX sex chromosome complement and the inverted 16 (indicated by the
abbreviation sl), but also have an additional chromosome 22. The second sideline consists of five cells with an XX sex
chromosome complement, the inverted 16, the additional chromosome 22 (indicated by the abbreviation sdl1), and
monosomy 7. Thus, we see that by examining the components of a reported karyotype using the above-outlined rules,
together with the abbreviations listed or in the nomenclature document itself, what initially might appear as an indecipherable
compilation of numbers and symbols becomes a concise, universal method of describing the results of a patient’s
chromosome analysis.

CHECK FOR UNDERSTANDING (25 minutes)

Activity 1

A. Define the following terms. Give the correct definition and symbol (with asterisk) for each of the following:
1. Neoplasia - ______________________________________________________________________________
_______________________________________________________________________________________
2. Clone - _________________________________________________________________________________
_______________________________________________________________________________________
3. Mainline* - ______________________________________________________________________________
_______________________________________________________________________________________
4. Stemline* - ______________________________________________________________________________
_______________________________________________________________________________________
5. Sideline* - ______________________________________________________________________________
_______________________________________________________________________________________
6. Composite* - ____________________________________________________________________________
_______________________________________________________________________________________
B. Chromosome Analysis. Completely describe the given karyotype below. Include in the description which clone is
the mainline, sideline, or stemline.

46,XY,t(8;21)(q22:q22) [5] / 45,-Y,t(8;21)(q22:q22) [10] / 48,-Y,+6,t(8 ;21),+18,-21,+mar [1] / 46,XY[5]

Description :_______________________________________________________________________________
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LESSON WRAP-UP (10 minutes)

A. Work Tracker

Mark (encircle) the session you have finished today in the tracker below. This is simply a visual to help you track how
much work you have accomplished and how much work there is left to do.

You are done with the session! Let’s track your progress.

B. Think About Your Learning

Let’s check your learning experience! Answer the following below.

What are the important lessons that you learned and what questions are you left with?
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(End of Session)

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