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2008, Volume 24, Number 3, Page(s) 140-146
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Diagnostic utility of cytokeratins 7, 10 and 20 in renal cell carcinoma and oncocytoma |
Saba KİREMİTÇİ1, Özden TULUNAY1, Sümer BALTACI2, Orhan GÖĞÜŞ2 |
1 Medical School of Ankara University, Departments of Pathology, ANKARA
2 Medical School of Ankara University, Departments of Urology, ANKARA |
Keywords: Cytokeratin 7, cytokeratin 20, cytokeratin, 10 renal cell carcinoma, renal oncocytoma |
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Renal cell carcinoma is the most frequent renal epithelial
tumor having various subtypes differing in their
prognosis and therapeutic response. In most cases it is
possible to distinguish subtypes on the basis of histology
alone, however, there are diagnostic difficulties for the
tumors having granular/eosinophilic cells which create
morphologic similarities not only between the subtypes
of renal cell carcinoma, but also, between a benign tumor
and renal oncocytoma. To achieve correct diagnosis,
immunohistochemical analysis focused on cytokeratin
(CK) proteins has been used increasingly. We examined
the diagnostic utility of CK7, CK10, and CK20 in
the classification of renal epithelial tumors based upon
an immunohistochemical analysis. The study included
tissue macroarray (4 mm) blocks of 83 renal cell carcinomas
(62 clear cell, 6 chromophobe, 13 papillary, 2
unclassified subtype), and 6 renal oncocytomas. Fuhrman
nuclear grade of the tumors, divided into low (grades
1, 2) and high nuclear grade (grades 3, 4) was negatively
correlated with CK7 expression (p=0.001). Diffuse
and significantly higher CK7 expression was found in
“non-clear cell” (chromophobe and papillary) subtypes
than in clear cell renal cell carcinomas (p=0.001). Of 6
renal oncocytomas, 4 was focally positive for CK7. The
results demonstrate that, diffuse and strong CK7 immunoreactivity
supports the diagnosis of “non-clear cell”
subtype versus clear cell renal cell carcinoma and renal
oncocytoma. Seldom CK20 reactivity of the tumors did
not show any significance, and the tumors were totally
unreactive to CK10 which eliminates diagnostic utility
of CK20 and CK10 in the classification of renal epithelial
tumors. |
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Renal epithelial neoplasms include
malignant renal cell carcinoma (RCC), the most common
malignancy of adult kidney 1, and benign
renal oncocytoma (RO). RCC comprises phenotypically
and genetically heterogeneous tumor
subtypes. International aggreement is achieved
on the histological classification of RCC
which is based on the light microscopic appearance
and also consistent with prevailing genetic
alterations 2. Tumor stage at presentation
and histologic nuclear grade (NG) have been
widely accepted as principal prognostic indicators
of RCC. Studies have shown that these tumors
have dictinctive microscopic, molecular
features and clinical presentations relevant with
metastatic tendency and potential response to
therapy. The results indicated a poorer survival
rate for patients with clear cell RCC (CRCC)
compared with patients with “non-clear cell”
RCC subtypes 3-6. The need for the application
of the appropriate therapies and the development
of targeted therapies for specific tumor
subtypes makes the accurate classification of renal
epithelial tumors more critical. Differential
diagnosis is generally easy for cases with characteristic
morphological features, but sometimes
differentiating RCC subtypes from each other
remains problematic on morphologic grounds.
On the other hand, a benign renal cortical
neoplasm, i.e. RO, which accounts for 3% to 7%
of renal cortical neoplasms, may closely mimic
a renal carcinoma in terms of histologic features
and clinical presentation. A careful microscopic
examination of a well sampled tumor will allow
correct diagnosis in majority of the cases, but
ancillary methods are necessary in certain situations.
A discriminatory immunoreactivity that
would confidently distinguish RCC subtypes
from each other or from RO has not been identified
yet. With this regard, we used various
CKs; CK7, CK10, and CK20, in the differentiation
of RCCs and RO which have led to various
conflicting results in the literature. |
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Abstract
Introduction
Methods
Results
Disscussion
References
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Renal epithelial tumors operated between
1995 and 2002 were retrieved from the archives
of Pathology Department. Hematoxylin and eosin
(HE) stained slides were reevaluated and the
tumors were reclassified according to the 2004
WHO classification 2. The clinical information
were obtained from the patients' medical records
and the macroscopic features of the tumors
were recorded from pathology reports.
The tumors were graded according to the Fuhrman's
grading system, and were grouped as low
NG (LNG; grades 1 and 2) or high NG (HNG;
grades 3 and 4). Immunohistochemical (IHC)
evaluation by a tissue macroarray technique
(TMA) was performed on 83 cases of RCC, and
6 cases of RO. TMAs were prepared using a manual
tissue-arraying instrument with a diameter
of 4 mm. For the “recipient” paraffin blocks the
representative areas of each tumor with characteristic
histomorphology and highest NG were
selected. Two to 5 tissue cylinders were punched
out from each “donor” paraffin blocks. A
total of 324 tumor tissue cylinders were mounted
into 27 ‘recipient' TMA blocks with a capacity
of 12 tissue cylinders of each. Antibodies
against CK7, CK10, and CK20 were reacted on
4 μm thick sections of TMA blocks, using standard
streptavidin-biotin peroxidase technique as
shown in Table 1. Counterstain was performed
with Mayer's hematoxylin, simultaneous positive
and negative controls were processed. For
each antibody presence of cytoplasmic and/or
membranous staining was considered positive.
The degree of intensity (I) of the staining was
semiquantitatively graded on a scale of 0 to 3;
none (0), mild (1), moderate (2), and strong (3),
and for the distribution (D) of the staining; none
(0), focal (<10%) (1), patchy (10-50%) (2), and
diffuse (>50%) (3). A staining score (IxD; 0-9)
was calculated. The result of staining was evaluated
as “positive expression” (stained) when
the staining rate of the marker was >1 or “negative
expression” (not stained) when it was ≤1.
Statistical analysis was performed using SPSS
9.0 for Windows program. The difference in numerical
data between groups was analysed using
Mann-Whitney U Test or T Test. The relationship
between IHC markers and histological variables
were evaluated using chi-square test. P value
of <0.05 was considered statistically significant
throughout the analysis.
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Abstract
Introduction
Methods
Results
Disscussion
References
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Among the RCC patients, there were 26
women (31.3%) with median age of 53.8 years
(26-75 years) and 57 men (68.7%) with median
age of 57.3 years (30-77 years) who were all
treated by radical nephrectomy. The median age
of all patients with RO treated by partial nephrectomy,
was 60.6 years (41-74 years). The reevaluation
of the HE stained slides of the tumors
revealed 62 CRCC (74.7%), 6 chromophobe
RCC (ChRCC) (7.2%), 5 type 1 papillary RCC
(PRCCT1) (6%), 8 type 2 papillary RCC
(PRCCT2) (9.7%), and 2 (2.4%) “unclassified”
RCC.
The expression of CK7 was different between
CRCC and “non-clear cell” RCC subtypes;
84.2% of “non-clear cell” RCCs (ChRCC,
PRCC) were found CK7 positive, while expression
rate was 27.4% (17 of 62 tumors) for
CRCCs (p=0.001). Of 13 PRCCs, 10 were found
to be CK7 positive (%76.9) while, all
ChRCCs were immunoreactive for CK7
(100%). The expression of CK7 was 100% and
62.5% (5 of 8 tumors) in PRCCT1 and PRCCT2,
respectively (Table 2). In ChRCC, and PRCC
the CK7 immunoreactivity was diffuse and
strong throughout the cytoplasm and in the cell
membranes of the tumor cells (Figure 1), whereas
the distribution was patchy with strong reactivity
in CRCC (Figure 2a, b). The immunoreactivity
of CK7 in RO was noted in 4 of 6 tumors
that was found only in scattered cells (Figure 2c, d). RO was entirely CK20 negative. CK20 was
widely negative in RCC subtypes. Out of 62
CRCCs, 3 tumors were CK20 immunoreactive
(4.8%) while only 1 PRCCT2 was positive
(5.2%) in the group of “non-clear cell” RCCs (1
of 19 tumors). In unclassified RCC group, one
of the two tumors was positive for CK7 and all
were negative for CK20. CK10 was entirely negative
in all tumor subtypes.
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Figure 1: CK7 expression pattern in “non-clear cell” RCC subtypes. Diffuse and strong CK7 expression in chromophobe RCC with intense membranous staining (a, b. peroxidase, x200, x400), in papillary type 1 (c, d. peroxidase, x100, x400), and in papillary type 2 RCC (e, f. peroxidase, x200, x400). |
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Figure 2: Patchy and strong (a, b. peroxidase, x200, x400), and scattered (c, d. peroxidase, x100, x400) CK7 expression in clear cell RCC and in renal oncocytoma, respectively. |
As shown in Table 3, CK7 expression was
related with nuclear differentiation in RCCs
(p=0.039). CK7 was positive in 52.5% of the
LNG and 30.2% of HNG tumors. Higher
percentage (61.8%) of CK7 positive tumors showed
LNG differentiation.
Click Here to Zoom |
Table 3: CK7 expression rates in RCC subtypes in relation with nuclear grades. |
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Abstract
Introduction
Methods
Results
Disscussion
References
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Cytokeratins are a family of intermediate
filaments that are characterize of epithelial differentiation,
and up to date at least 20 distinct
CK subsets have been identified expressed by
different epithelia and their neoplastic transformations
7. Majority of the studies on CK expression
of renal tissues and renal tumors have
examined a limited CK panel such as CK7 and
CK20. There have been conflicting results on
the expression of CK7 in renal epithelial tumors
in the literature while some authors have recommended
CK7 as a differential marker in distinguishing
ChRCC from RO 8-10, the others
11-13 may insist on its role in the differentiation
of “non-clear cell” RCC and RO from CRCC.
Reports on the CK7 expression of CRCC have
suggested a consensus of general negativity
with the positivity in a range of 4.8-10.5%
12,14. PRCC and ChRCC were reported to have
extensive CK7 expression with a range of 43-100% for ChRCCs 10,15,16, and a superiority
of expression for PRCCT2 over PRCCT1
13,14. Reports on the expression of CK7 in
RO also had conflicting results with focal, diffuse
and negative staining patterns 8,10,14,16,17.
In the present study differential diagnostic value
of CK7 was exhibited between CRCC and “nonclear
cell” RCC subtypes. “Non-clear cell” RCCs
had significantly higher, more diffuse and intense
CK7 expression rates (100% for ChRCCs and
76.9% for PRCCs), while the positivity rate was
27.4% for CRCCs demonstrating patchy and intense
expression. Not only the percentage of the
immunoreactive cells, but also the staining pattern
with patchy distribution differed between
these subtypes. The positivity rate of CK7
(27.4%) in the CRCC group is slightly higher
according to the literature 8,12, but the relation
with the other subtypes retains its significance.
Skinnider et al 8, and Mazal et al 12 reported
CK7 positivity rates for CRCC, ChRCC,
PRCC as 20%, 73%, 86%, and 8%, 88%, and
77%, respectively. We conclude that; because
both CRCC and non-clear RCCs may reveal the
absence of CK7, strong and diffuse CK7 expression
pattern becomes meaningful to support
“non-clear cell” RCC diagnosis versus CRCC.
This staining pattern may also indicate ChRCC
diagnosis resembling RO, which has been widely
reported to show focal scattered staining or
absence of expression. The study revealed a
scattered focal immunoreactivity of CK7 in 4 of
6 ROs, while the remaining two was diffusely
negative. Skinner et al 8 reported a negative
CK7 staining in 10 ROs whereas a low rate of
immunoreactivity in 66 ROs has been shown by
Langner et al 14. Focal scattered staining pattern,
they had found, was consistent with our
observation in ROs (Figure 2).
CK7 immunoreactivity in PRCC has commonly
been reported with differing staining rate
and intensity in type 1 and 2 tumors 13,14.
Both studies have revealed a strong expression
of the marker in the relatively benign PRCCT1,
compared with the weak expression in the more
agressive type 2 tumors. In the present study,
CK7 was immunoreactive in total of 5 PRCCT1
tumors and 5 of 8 PRCCT2 tumors with a diffuse
pattern and strong intensity. Although this
diffuse and strong expression of CK7 in
PRCCT2 is not consistent with the previous reports,
the present study revealed a significant
correlation between CK7 expression and nuclear
differentiation (p=0.039), which supports the
relation of CK7 expression with tumor aggressiveness.
CK7 was expressed in 52.5% (20 of 39
tumors) of the tumors with LNG, and 30.2% 13
of 42 tumors) of the tumors with HNG. This
strong association may be the reason for the
conflicting results in the literature for the differentiation
of RCC subtypes. We may refer that
if CK7 expression is compared between the
subtypes with the same NG, more significant
and persuading results would be achieved, and it
would be more meaningful in diagnosing tumor
subtypes, regardless of negative impact of cellular
differentiation.
CK20 has been shown to have a limited
expression in normal tissues and neoplasms.
CK20 expression in renal tubular epithelial tumors
has been seldomly reported, and identified
in 0-7.7% of RCCs 9,14,15,19. Langner et al
14 have reported a general lack of CK20 expression
in a series of 233 renal tumors, with a
positivity in only 2 of 8 PRCCT2s. Kim et al 9
have observed CK20 immunoreactivity in 4 of
20 PRCCs, without indicating their subtypes.
Both studies have revealed the absence of CK20
in RO 9,14. Our results are similar to those found
in these reports in that we detected only one
PRCCT2 showing CK20 expression, and negativity
for all cases with RO. But in our series in
a total of 62 CRCCs, more than 50% of cells of
3 tumors were moderately stained with CK20.
This confusing result shows the possibility of
positive CK20 expression in CRCC. Literature
findings have also shown confusing results for
RO, and paucity of studies have reported CK20
expression in Ross. Stopyra et al have found the
coordinate staining of CK7 and CK20 as a useful
diagnostic tool in distinguishing RO from
RCC 20. In our opinion, CK20 does not appear
to show a consistent immunoreactivity neither
in RCC nor in RO, and does not seem to be
a reliable differentiating marker for renal tubular
neoplasms.
Literature contains scarce number of reports
for CK10 expression in renal epithelial tumors
which absolutely have shown the absence
of the marker 14. None of the tumors in our
study had immunoreactivity with CK10, as well.
Thus CK10 seems to have no role in renal epithelial
tumor differentiation.
We conclude that, CK7 immunohistochemistry
is a useful diagnostic tool in distinguishing
“non-clear” RCC from CRCC with diffuse
and strong expression of CK7 supporting “nonclear”
RCC diagnosis. The extent of CK7 expression
may indicate the aggressiveness of the
tumor, and with this regard, better organized
studies consisting of larger series of RCCs with
the same NG are needed to be evaluated. CK20
and CK10 immunohistochemistry seem to be an
unreliable analytical method in differentiating
renal tubular neoplasms. |
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Abstract
Introduction
Methods
Results
Discussion
References
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Abstract
Introduction
Methods
Results
Discussion
References
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