2014, Volume 30, Number 3, Page(s) 201-205
TTF-1 may not be a Reliable Marker for Differentiating Metastasis from Brain Tumors
Betül ÜNAL1, Ţenay YILDIRIM2, Cem SEZER2, Dinç SÜREN2
1Department of Pathology, Akdeniz University, Faculty of Medicine, ANTALYA, TURKEY
2Antalya Education and Research Hospital, ANTALYA, TURKEY
Keywords: TTF-1 protein, Brain neoplasms, Astrocytoma
TTF-1 is widely used as an immunohistochemical
marker of lung and thyroid tumors. However, TTF-1 expression has
been described in tumors from other sites. The presence of TTF-1
expression in primary brain tumors is largely unclear and has not
been clearly specified yet. We characterized expression of two TTF-1
clones in primary brain tumors with relevance to tumor types and
Material and Method: We studied immunohistochemistry with
tissue micro-array, using both clones (8G7G3/1 and SPT24) in
45 primary brain tumors of different types and grades. Our cases
consisted of 1 grade I, 7 grade II, 4 grade III, 20 grade IV astrocytic
tumors; 9 meningiomas, 2 oligodendrogliomas, 1 schwannoma and 1
Results: We have found TTF-1 nuclear staining using the SPT24 clone
in 4 cases (3 cases were grade IV and 1 was grade III). Focal and weak
staining was seen in three cases and moderate-strong and diffuse
staining was seen in one case. All the tumors were negative with clone
8G7G3/1. Clone SPT24 was more sensitive but less specific.
Conclusion: TTF-1 can also be expressed in primary brain tumors,
particularly grade III to IV tumors. TTF-1 expression was a rare
finding in previous studies, however strong and diffuse staining was
not observed until today. We think that TTF-1 nuclear expression in
high-grade astrocytic tumors cannot rule out primaries even when
diffuse and strong staining. Clinical and pathological parameters
should be evaluated together.
Thyroid transcription factor-1 (TTF-1) is a 38 kDa DNAbinding
protein containing 371 amino acids. It is essential
for the development and differentiation of the thyroid, lung
and ventral forebrain1
. In the lung, TTF-1 is expressed
in type II pneumocytes and Clara cells and regulates
Surfactant B protein production2
. However it is expressed in follicular cells and C cells and regulates the production
of thyroglobulin and thyroperoxidase3
. In the brain,
TTF-1 is expressed in the neurons of the hypothalamus and
controls the migration of telencephalic interneurons4
TTF-1 is widely used as an immunohistochemical marker
of lung and thyroid tumors. However, TTF-1 expression
has been described in tumors from other sites, particularly colorectal carcinoma, gynecological tumors, urothelial
carcinoma, prostate, stomach, and salivary gland carcinoma
and primary central nervous system tumors5-8. The
presence of TTF-1 expression in primary brain tumors is
largely unclear and has not been clearly specified yet.
Two antibody clones are currently widely used for TTF-1
demonstration, 8G7G3/1 and SPT24. Many studies have
demonstrated that clone SPT24 is more sensitive but less
specific than clone 8G7G3/15,9-11.
In the current study, we investigated the expression of TTF-
1 in primary brain tumors of various types and grades, using
both clones, 8G7G3/1 and SPT24, and compared them with
each other. We aimed to clarify the usefulness of TTF-1 for
differentiating metastasis from primary brain tumors.
Formalin-fixed, paraffin-embedded tissue
blocks of primary brain tumors were selected from archives
of Antalya Training and Research Hospital dated 2008 to
2013. A total of 45 tumors were included in the study. The
tumors were classified histologically according to the World
Health Organization classification of primary brain tumors.
Tissue Microarray Technique: Tissue microarrays were
constructed from archived formalin-fixed, paraffinembedded
tissue blocks using a semi-automatic tissue
arrayer (Minicore, Alphelys). Tissue cylinders with a
diameter of 2 mm were punched from the tumoral area of
the donor block and were transferred to a recipient paraffin
block. Sections of 4-μm thickness were cut from tissue
Immunohistochemistry: Tissue microarray sections were
dewaxed in xylene, rehydrated in alcohol, and immersed
in 3% hydrogen peroxide for 10 minutes to suppress
endogenous peroxidase activity. Antigen retrieval was
performed by heating each section for 30 minutes in 0.01
mol/l sodium citrate buffer (pH 6.0). After three rinses
in phosphate-buffered saline (PBS) for 5 minutes, each
section was incubated for 1 hour at room temperature with
TTF-1, clones SPT24 (dilution 1:25, Novocastra Lab. Ltd.,
Newcastle Upon Tyne, UK) and 8G7G3/1 (Dilution 1:1OO,
Dako North America, Inc., Cartinteria, CA); washed three
times in PBS for 5 minutes; incubated with horseradish
peroxidase labeled rabbit anti-mouse immunoglobulin;
washed three times; and incubated with a solution of
diaminobenzidine (DAB) at room temperature to visualize
The immunohistochemical stains of both clones were
scored as positive or negative. A positive score was based
on focal-diffuse, weak-moderate-strong, nuclear staining.
In our study, there were 18 (41%) female and 26 (59%)
male patients, with an age range of 37 to 83 years. Our cases
consisted of 1 grade I, 7 grade II, 4 grade III, 20 grade IV
astrocytic tumors; 9 meningiomas, 2 oligodendrogliomas,
1 schwannoma and 1 medulloblastoma. TTF-1 expression
was seen in a small subset of primary brain tumors with
clone SPT24. The primary brain tumor types, which showed
positive immunostaining for TTF-1 using the SPT24 clone
(4 of 45 cases, 8.8%), were grade III-IV glial astrocytic
tumors,. All 45 tumors were negative when stained with
clone 8G7G3/1. The positive stained cases consisted of 3
(6.6%) case grade IV glial tumors (glioblastoma) and 1
(2.2%) case grade III glial tumor (anaplastic astrocytoma).
Focal and weak expression was found in 3 cases and 1
glioblastoma showed diffuse and strong staining (Figure
). Nonspecific cytoplasmic staining was observed in
two tumors of which one was meningioma and the other
was glioblastoma (Figure 2
). Among grade III to IV glial
tumors, TTF-1 expression was found in 4 of 45 (8.8%) cases
whereas none of the grade I to II glial tumors expressed
TTF-1. The other primary brain tumors were all negative for
TTF-1 using the two clones, 8G7G3/1 and SPT2 (Table I
Click Here to Zoom
|Figure 1: TTF-1 expression in astrocytic tumors (grade III-IV) A)
Nuclear staining of tumor cells in glioblastoma was noted using
the SPT24 clone (TTF-1; x400). B) Weak focal nuclear staining
(TTF-1; x400). C) Moderate diffuse nuclear staining, x400. The
same cases were negative with the 8G7G3/1 clone.
Click Here to Zoom
|Figure 2: Nonspecific cytoplasmic staining in meningioma (TTF-
Click Here to Zoom
|Table I: Summary of immunohistochemistry results of TTF-1,
clones SPT24 and 8G7G3/1
TTF-1 expression was first described by Lazzaro et al. in the
fetal rat lung, thyroid tissue and neurohypophysis in 199116
. TTF-1 is widely used in thyroid and lung tumors in
. TTF-1 is a very important marker for
distinguishing primary pulmonary adenocarcinomas from
metastatic tumors. Jerome MV et al.17
TTF-1 expression in lung carcinomas, particularly small
cell carcinoma, adenocarcinoma and non-mucinous bronchioloalveolar carcinoma, but no positivity was
described in squamous cell carcinoma and mucinous
bronchioloalveolar adenocarcinoma. The lung is a common
site of metastatic carcinomas. The specificity of TTF-1 for
pulmonary lesions has been demonstrated in many studies18
. TTF-1 is a reliable marker for the lung and thyroid,
although TTF-1 expression was also identified in urothelial
carcinoma, prostate, stomach, salivary gland carcinomas6,
and uterine tumors21
. In addition, TTF-
1 expression was described in primary central nervous
system tumors in a few studies5,12-15
The two monoclonal antibodies of TTF-1 that are currently
widely used for immunohistochemistry are 8G7G3/1 and
SPT24. Clone 8G7G3/1 has been used since 1996, whereas
clone SPT24 became available later5. Most studies have
shown high specificity for clone 8G7G3/1, while clone
SPT24 seems to have higher sensitivity but less specificity10. Matoso et al.6 found 72% TTF-1 positivity with
SPT24 versus 65% positivity with 8G7G3/1 in 185 lung
adenocarcinomas. Penman et al.11 reported TTF-1
positivity in 3 out of 6 colorectal carcinomas using clone
SPT24 while all of the cases were negative with the other
TTF-1 expression in primary brain tumors was a rare
finding in previous studies. As far as we are aware, only 5
studies of TTF-1 expression in primary brain tumors have
been published until today12-15. These studies have
reported TTF-1 expression with divergent results. The
problem seems to be the use of different clones. However
only one study, by Kristensen et al., analyzed TTF-1 with both clones, 8G7G3/1 and SPT24. Similarly, we tested
primary brain tumors of various types and grades using
both TTF-1 clones, 8G7G3/1 and SPT24, and compared
them with each other. Our study is the second study using
both clones of TTF-1 simultaneously in primary brain
tumors to the best of our knowledge.
In chronological order, Zamecnik et al.12 tested 73
primary brain tumors using clone 8G7G3/1 and TTF-1
was positive in 2 ependymomas. Prok and Prayson13
tested 50 glioblastomas using the same clone and none was
positive for TTF-1. Later, Galloway and Sim14 found
TTF-1 expression in 13 out of 26 glioblastomas using clone
SPT24. Lee et al.15 studied 17 sellar/supracellar tumors
using the SPT24 clone, and all of them were positive.
Finally, Kristensen et al.5 analyzed TTF-1 expression in a
series of 155 central nervous system tumors comparing the
8G7G3/1 and SPT24 clones. TTF-1 expression was observed
in 13 cases (8%) with the SPT24 clone. Expression was
found in 10 grade III to IV tumors, 1 central neurocytoma,
1 ependymal tumor and 1 choroid plexus tumor.
In our study, TTF-1 was positive in 4(8.8%) cases using
SPT24 clone and all of the tumors were negative with clone
8G7G3/1. During TTF-1 determination using SPT24 we
found weak-focal nuclear staining in 3(6.6%) cases and
strong-diffuse staining in 1(2.2%) case in our TMA slides.
Three (75%) out of 4 case were glioblastoma (grade IV) and
1(25%) case was anaplastic astrocytoma (grade III). This is
concordant with Kristensen et al. and Galloway and Sim.
Kristensen et al. found weak to moderate and focal TTF-1
staining based on clone SPT24 in 13 of 155 cases and 6 of 36
cases were positive in glioblastomas. In addition Galloway
and Sim found TTF-1 expression in 13 of 26 glioblastomas
with clone SPT24. In both of the studies no positivity found
in all cases with clone 8G7G3/1. Neither Prok and Prayson
nor Zamecnik et al. found any expression for TTF-1 among
glioblastomas and astrocytic tumors using clone 8G7G3/1.
Furthermore all these findings are in concordance with our
As far as we know, there are 5 studies on TTF-1 expression
in primary brain tumors in the literature. However only
one study, by Kristensen et al., analyzed TTF-1 with both
clones, 8G7G3/1 and SPT24. This is the second study that
used both two clones and compared them with each other.
In conclusion, TTF-1 can also be expressed in primary
brain tumors, particularly grade III to IV tumors. Boggaram
V reported that TTF-1 is essential for development of
the ventral forebrain1 and can therefore be associated
with TTF-1 expression in primary brain tumors. TTF 1 expression was rarely reported in previous studies but
strong and diffuse staining had not been observed until now.
We suggest that TTF-1 nuclear expression in high-grade
astrocytic tumors cannot rule out primaries even if there is
diffuse and strong staining. Clinical and histopathological
parameters should be evaluated together for the differential
diagnosis. More studies will be needed to better understand
the importance of TTF-1 immunoreactivity in primary
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