Moderators: Dr. Gregor Mikuz and Dr. Victor E. Reuter
Section 3 -
Cytogenetics of Germ Cell and Sex Cord-stromal Tumors of the Testis
Gregor Mikuz and Irmgard Verdorfer
Institute of Pathology
Innsbruck , Austria
Since the advent of cytogenetic analysis, knowledge about fundamental aspects of cancer biology has
increased allowing the process of cancer development and progression to be better understood. Many
tumors show specific gene mutations, amplifications, deletions and translocations (Ewing sarcoma,
synovial sarcoma, translocation carcinoma of the kidney etc.) as well as a specific gain or loss of
entire chromosomes. These chromosomal aberrations can be used in the morphological diagnostic in cases
with ambiguous morphology or in completely undifferentiated tumors.
Classical cytogenetics of solid tumors has been extremely difficult in the past because only living
cells in the metaphase could be analysed, which means that tumor cells have to be cultivated. Modern
molecular techniques allow cytogenetic analyses even in interphase cells and in paraffin embedded tissue.
For the analysis of chromosomes the most used methods are the fluorescence in situ hybridization (FISH)
and the comparative genomic hybridization (CGH). FISH is particularly useful for gene mapping and for
identifying chromosomal abnormalities, whereas, CGH allows the genome wide detection of numerical
chromosomal changes without the need for metaphase spread of tumor cells.
Cytogenetic analyses of testicular germ cell tumors (TGCTs) of the testis are of scientific interest,
because they allow a deeper insight into their histogenesis. For diagnostic purposes the cytogenetic of
TGCTs is, however, useless because, with few exceptions, the chromosomal aberrations are not specific for
the single tumors. Thus the morphological diagnosis of TGCTs is still based on their morphological
In 1982 Atkin and Baker  described a chromosomal change, that they supposed to be specific for
testicular tumors – the isochromosome i(12p), which shows a gain of the short arm (Fig.1).
Fig.1 Isochromosome i(12p) left CGH preparation with gain of short arm (short bar) and
right the classical metaphase karyogram.
is present in about 80% of the TGCT  – more often in non seminomatous germ cell tumors
(NSGCT) than in seminomas. Extragonadal as well as ovarian GCTs also show this chromosomal anomaly.
TGCT without i(12p)
have an amplification of genetic material of chromosome 12  The gain of genetic
material on chromosome 12 seems to be crucial for the transition from the undifferentiated intratubular
germ cell neoplasia to invasive GCTs
Classic seminoma are aneuploid tumors. Previous reports on diploid cases
detected by flow cytometry have most likely been caused by extensive lymphocytic infiltration .
Cytogenetic studies almost constantly revealed numerical chromosomal aberrations in seminoma. CGH
analysis show chromosomal imbalances including gain of parts of 7,8,12,14 and X, and losses of parts of
3,4,5,10,11,16,18,22,and Y .
Fig.2. CGH of a classic (blue bars ) – and
spermatocytic seminoma (pink bars). The bars on the right mean gain, those on the left losses of
Of all TGCT spermatocytic seminoma show the most specific chromosomal
imbalances – the gain of chromosome 9
which is related to the gene DMRT1. Based on the region of
amplification defined on 9p and the associated expression plus confirmatory immunohistochemistry, DMRT1
(a male-specific transcriptional regulator) was identified as a likely candidate gene for involvement in
the development of spermatocytic seminomas . NSGCT show very
heterogeneous patterns of chromosomal imbalance. In combined tumors (embryonal carcinoma, teratoma and
yolk sac tumor) all histological components show gains and losses in a very variable amount. Most
frequent gain of parts of 1q, 17, 19p, 20q and 22, and losses of parts of 4, 5, 9p, 13 and 18q have been
observed . In our material seminoma combined with embryonal carcinomas show a marked gain of X
Since sex cord-stromal tumors of the testis account for
3-4% of all testicular neoplasms the rarity
of genetic analysis of such tumors is not really
surprising. Leydig cell tumors (LCT) of the testis represent only
1-3% of testicular neoplasms. These tumors occur over a wide range of age, from childhood to senior
adulthood. They are most common in the third to sixth decade, approximately one fourth of the reported
FISH of Leydig cell tumors: gain of X chromosome before puberty. The histomorphology of these tumors
is well known but no reports of cytogenetic data are available in literature. In our material the
majority of the 25 analyzed LCT 
showed chromosomal imbalances (21/25, 84%). The total number of DNA
imbalances per tumor varied from case to case. A high genetic heterogeneity and involvement of
chromosomes were found. Gain on chromosome X (Fig.3) was detected at a high frequency (56%), followed by
gain of chromosome 19 or 19p in 28% and losses on material of chromosome 1 (24%) and 8 or 8p in 16%. The
frequent finding of gain of chromosome X by CGH in the present study was confirmed by FISH, with mainly
two copies of chromosome X, showing XXY/XX/XXYY or XXY/XXYY mosaicism. The fact that in 56% of our cases
of LCT showed gain on chromosome X is of interest, because overexpression of chromosome X was also a
frequent observation in seminomas, nonseminomas and spermatocytic seminomas (21-23). The biological and
clinical significance of numerical increase in X chromosomes in testicular germ cell tumors was suggested
by enhanced expression of the 2 X-linked oncogenes ARAF1 and EKL1 .
Sertoli cell tumors (SCT) are even more rare than LCT. Their morphology is also extremely
heterogeneous. In most cases, however, a tubular differentiation permits a correct classification. Even
in less differentiated cases with solid growth patterns some tubules can be detected. In cases with
entirely solid pattern the diagnosis is made when "the appearance is inconsistent with any other
plausible diagnosis"  , which is also supported by appropriate immunostains.
Cytogenetic data about human SCT of the testis are very rare. Aly et al.  reported loss of
chromosome Y as the sole aberration in a 5-year-old boy with malignant SCT.
Fig 4. CGH of Sertoli cell tumors – right bars gain, left bars losses
Few genetic data are reported in Sertoli cell tumors of the ovary
Only a single CGH
analysis of an ovarian SCT is reported in the literature  with amplification of 1q21.3.31, 6q and
deletion of 7q32-35. Formation of an i(1q)
was reported  as the sole karyotypic abnormality in a
peritoneal metastasis of an ovarian Sertoli cell tumour.
Gain on copy number of chromosome X (Fig.4), was detected as the most frequent aberration in our study
(58%) and was confirmed by FISH . In most of the analysed tumour tissues we found tripartite
mosaicisms (XY/XXY/XXYY). The loss of the entire or part of chromosome 2 is the second most frequent
(30% of cases) aberration in our material.
Two cases of malignant Sertoli-Leydig cell tumors of the testis and one ovarian SLCT with benign
behavior showed copy number changes of chromosome 1, 8, 9p, 10, 11, 12, 16, 19, 22 and X .
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- Verdorfer I, Höllrigl A, Strasser U, Susani M, Hartmann A, Rogatsch H, Mikuz, Molecular cytogenetic characterisation of sex cord tumors: CGH analysis in Sertoli cell tumors of the testis. - submitted.
- Verdorfer I, Horst D, Höllrigl A, Rogatsch H, Mikuz G, Sertoli-Leydig cell tumors of the ovary and testis:A molecular cytogenetic study - Virchows Archiv - in press