PART ONE
General Cytology
Fig. 2.20
Illustration of the
FICTION
method on
multiple myeloma cells.
The plasma cells are detected with the use of antibodies directed against the
cytoplasmic immunoglobulins A, or K. these antibodies are colored with fluorochrome AMCA (blue color). (A) Two plasma cells with deletion of the
p53
locus
(chromosome 17p13) demonstrated by the absence of one red signal, whereas the existence of both chromosomes 17 is confirmed by a specific chromosome
17 centromeric probe (green signals). (B) plasma cell harboring the
FGFR3/M MSET-IgH
fusion genes corresponding to the t(4;14)(p16;q32) translocation. the
two yellow fusion signals are due to red and green signals relocating next to each other, and indicate the
FGFR3/M MSET-IgH
fusion gene and its reciprocal. the
green and red signals correspond to remaining normal
IgH
and
FG FR3/M M SET
genes respectively.
A recent study aimed at comparing the utility of I-FISH and
flow cytometry immunophenotyping (FCM) in a series of FL
and DLBCL.71 They found that detection of t(14;18) by FISH was
a slightly more sensitive (85%) diagnostic marker than identi-
fication of the typical CD19+/CD10+ immunophenotype pro-
file by FCM (75%). FISH appeared to be more sensitive because
it could also detect FLs with an atypical CD19+/CD10- pattern.
In the same study, a
BCL2
gene rearrangement was detected by
FISH in 29% of DLBCL cases, whereas FCM was able to iden-
tify a CD10+ monoclonal population in only 23% of such lym-
phoma cases. I-FISH appeared thus to be slightly more sensitive
than FCM in identifying germinal center B-like DLBCL.
Sarcomas
Most (if not all) chromosomal translocations described in soft-
tissue sarcomas (STS) are detectable by I-FISH. This method
is thus particularly useful in diagnostically difficult cases such
as small blue cells tumors. Several studies aimed at compar-
ing the efficiency of both reverse transcriptase (RT)-PCR and
FISH techniques for a molecular diagnosis in sarcoma.79,80
Both methods were complementary and had their own advan-
tages and disadvantages in terms of specificity and qualitative
and quantitative sensitivity. However, the FISH break-apart
approach appears to be very practical in that the use of a single
break-apart probe can recognize each specific translocation
such as the t(X;18) in synovial sarcoma, the t(2;13) or t(1;13)
in alveolar rhabdomyosarcoma, and the t(12;16) in myxoid
liposarcoma. The potential disadvantage of such an approach
would be its inability to distinguish Ewing/PNET from other
sarcomatous types harboring EWS gene rearrangements (see
Table 2.2) since the partner gene is not detected. In most cases,
these neoplasms are nevertheless distinguishable from each
other on the basis of clinical data or immunocytochemical dif-
ferences.
Several studies have demonstrated the usefulness of cyto-
genetics81,82 or I-FISH83-85 as an adjunct in making a definitive
diagnosis of sarcoma by FNA. As our knowledge about the spe-
cific chromosomal abnormalities associated with sarcoma is
constantly increasing, there is good hope that I-FISH will allow
accurate diagnosis on more cases investigated by FNA, obviating
open surgical biopsy preceding therapy.
Multiple Myeloma
Multiple myeloma (MM) is characterized by numerous chro-
mosomal abnormalities which have been shown to significantly
impact survival in patients with such disease.86 The most rele-
vant alterations include hyperdiploidy, monosomy 13/deletion
13q14, deletion 17p, t(11;14)(q13;q32), and t(4;14)(p16;q32)
translocations, giving rise to the
BCL1-lgH
and
FGFR3/MMSET-
IgH
chimeric genes, respectively. Hyperdiploidy is associated
with a favorable prognosis but all other abnormalities represent
unfavorable parameters, among which the t(4;14) and dele-
tion17p appear to be the most important. Their identifications
have implications for the design of risk-adapted treatment strat-
egies. Historically, testing for abnormalities in MM was based
on conventional chromosomal analysis performed on bone
marrow, but results were often falsely normal since the actively
normal myeloid cells were analyzed rather than the monoclonal
plasma cells, which infrequently enter mitosis. Standard FISH
studies were thus employed to detect the classical abnormali-
ties associated with MM. Again, erroneously normal results were
most often obtained since this method is not able to distinguish
between normal cells and small clones of monoclonal plasma
cells. A novel FICTION method, which is a combination of
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