Journal of Cancer Therapy, 2012, 3, 836-840
http://dx.doi.org/10.4236/jct.2012.325106 Published Online October 2012 (http://www.SciRP.org/journal/jct) 1
Clinicopathological Characteristics of Basal Type Breast
Cancer in Triple-Negative Breast Cancer
Goro Kutomi1, Tousei Ohmura1, Yasuyo Suzuki1, Hidekazu Kameshima1, Hiroaki Shima1,
Tomoko Takamaru1, Fukino Satomi1, Seiko Oto ko zawa2, Mitsuru Mori2, Koichi Hirata1*
1First Department of Surgery, School of Medicine, Sapporo Medical University, Sapporo, Japan; 2Department of Public Health,
School of Medicine, Sapporo Medical University, Sapporo, Japan.
Received August 28th, 2012; revised September 25th, 2012; accepted October 3rd, 2012
ABSTRACT
Background: Triple-negative breast cancer (TNBC) is defined by the absence of estrogen receptor (ER), progesterone
receptor (PgR) and human epidermal growth factor 2 (HER2) expression. Patients with TNBC derive no benefit from
molecularly targeted treatments, such as endocrine therapy or trastuzumab, as they lack the appropriate targets for these
drugs. TNBC is characterized by its biological aggressiveness and poor prognosis, and consists of two subtypes, basal
and nonbasal. The purpose of our study is to differentiate the clinicopathological characteristics of the two subtypes.
Methods: 367 patients with primary breast cancer were recruited from April 2004 to December 2010 at 1st Department
of Surgery, Sapporo Medical University. ER, PgR, and HER2 status were evaluated in all cases. Moreover, we classi-
fied TNBC into basal, nonbasal subtypes on the basis of immunohistochemical staining of epidermal growth factor re-
ceptor (EGFR), cytokeratin (CK) 5/6. Basal type was defined as CK5/6-positive and/or EGFR-positive, and nonbasal
type was defined as no expression of these two markers. Results: Breast cancer subtypes by molecular classification
were Hormone receptor (HR)-positive/HER2-negative (61%), HR-positive/HER2-positive (10%), HR-negative/HER2-
positive (14%), and HR-negative/HER2-negative (15%). There was no difference between the basal type and the non-
basal type in clinicopatho logical factors. But, the basal type was significantly associated with Ki67 labeling ind ex (p =
0.0002), p53 expression (p = 0.047), and BRCA1 expression (p = 0.03). Further, patients with the basal type TNBC
showed a shorter overall survival (p = 0.032) than did patients with the nonbasal type. Conclusion: Classification of
TNBC subtypes by EGFR, CK5/6 is a very useful prognostic factor, and highlights the need for the development of an
adequate new strategy for th e basal type TNBC.
Keywords: Triple-Negative Breast Cancer; Basal Type; EGFR; CK5/6
1. Introduction
Breast cancer is the most common female cancer. It
affects more than 1 million women worldwide and about
400,000 patients die due to this disease every year. In
Japan, more than 60,000 women are affected by this
cancer and more than 12,000 patients die due to the
disease each year. Recently, gene expression studies have
identified several major subtypes of breast cancer.
Triple-negative breast cancer (TNBC), characterized by
the absence of estrogen receptor (ER) and, progesterone
receptor (PgR) expression and no overexpression of epi-
dermal growth factor receptor 2 (HER2), is typically as-
sociated with a poor prognosis, due to the aggressive
tumor phenotype. Further, TNBC is, only partially res-
ponsive to chemotherap y and presents a lack of clinically
established targeted therapies. Consequently, only con-
ventional chemotherapy is currently used in clinical prac-
tice and it effectiveness is limited [1]. Moreover, TNBC
consist of two subtypes; basal and nonbasal type. The
terms TNBC and basal type often are used inter-
changeably as there is an overlap in the biological and
clinical characteristics of these tumors [2]. Basal type is
similar to triple-negative breast cancer because almost all
basal type do not express ER, PgR, and HER2. It has
aggressive characteristics, such as high histological grade,
p53 mutation, epidermal growth factor receptor (EGFR)
overexpression. Some authors have claimed that the
basal type is composed almost entirely of TNBC, and
therefore, the TNBC phenotype could reliably be used as
a surrogate for the basal type [3]. However, Rouzier [4]
et al. demonstrated that ER, and HER2 expression were
seen in 5% and 14%, respectively, of basal type that had
been diagnosed by gene expression profiling. Therefore,
TNBC is not similar to basal type. In this study, we
*Corresponding a uthor.

Clinicopathological Characteristics of Basal Type Breast Cancer in Triple-Negative Breast Cancer 837
examined the clinical and pathological characteristics of
the two TNBC subtypes. Basal type has more aggressive
phenotype compared with nonbasal type. For example,
basal type had higher rates of node positive than
nonbasal type. In pathological perspectives, basal type
was positively correlated with expression of p53, Ki67
and BRCA1.
2. Materials and Methods
Tissue samples were obtained from 365 patients diag-
nosed with breast cancer from April 2004 to December
2010 at 1st Department of Surgery, Sapporo Medical
University, Japan. Other background data for the TNBC
patients are shown in Table 1. The expression of ER,
PgR, HER2, EGFR, CK5/6, and other biological markers
was determined immunohistochemically using paraffin-
embedded tissue specimens. Table 2 summarizes all the
antibodies, dilutions, and cutoff values used for this
analysis. The expression of ER or PgR was designated
as positive when at least Total score 3 on Allred score
showed positive staining. Tumors that were immunohisto-
chemically scored 3+, or scored 2+ and were FISH-
positive, were regarded as HER2-positive. The expres-
sion of Ki67 was designated as positive when at least
20% of stained nuclei in 1,000 tumor cell nuclei [5]. The
expression of CK5/6, EGFR, p53, SOX2, BRCA1 was
designated as positive when at least 10% of the tumor
cells showed positive staining (cytoplasmic staining for
CK5/6, EGFR, SOX2, BRCA1; nuclear staining for p53 )
(Figure 1).
This study was approved by the ethics committee in
Sapporo Medical University Hospital.
There are non-financial competing interests in this
study.
3. Statistical Analysis
The chi-squared test and unpaired t-test were used for
the analysis of two unpaired samples. Disease-free sur-
vival and overall survival rates after surgical resection
were calculated by the Kaplan-Meier method, and dif-
ferences in survival curves were assessed by the log-rank
test. The Cox proportional hazards model was used for
multivariate analysis. All analyses were performed with
SPSS version 18.0 (SPSS Inc, Chicago IL). A p value of
less than 0.05 was regarded as statistically significant.
All statistical tests were two- sided.
4. Results
Triple-negative breast cancer was diagnosed in 54
(15.3%) of the 365 cases of operable breast cancer. The
HR(+)/HER2(–), HR(+)/HER2(+), HR(–)/HER2(+), and
TNBC phenotypes were identified in 224 (61%), 36
Table 1. Clinicopathological factors in 365 primary breast
cancers.
Age (years), mean ± SD 57.4 ± 12.5 yes rs
Menopause
Pre 94 (25.7%)
Post 271 (74.3%)
Tumor size(cm) , mean ± SD 3.0 ± 2.6
Nodal status
(–) 252 (69.0%)
1 - 3 61 (16.7%)
4~ 52 (14.3%)
Stage
Ⅰ 129 (35.3%)
Ⅱ 166 (45.5%)
Ⅲ 48 (13.2%)
Ⅳ 22 (6%)
Histology
Pap-tub 130 (35.6%)
Sol-tub 39 (10.7%)
sci 111 (30.4%)
Others 85 (23.4%)
NG
1 92 (25. 2%)
2 121 (33.2%)
3 152 (41.6%)
ER or PgR
(+) 297 (81.4%)
(–) 68 (18.6%)
HER2
(+) 90 (24.1%)
(–) 275 (4.5%)
Pap-tub, papillotubular carcinoma; sol-tub, solid-tubular carcinoma; Sci,
scirrhous carcinoma; NG, nuclear grade; ER, estrogen receptor; PgR, pro-
gesterone receptor; HER2, human epidermal growth factor receptor-2.
(10%), 51 (14%), 54 (15%) of the breast cancers, res-
pectively . TNBC was classified into tw o subtype s, basal
(39/54, 72.2%) and nonbasal (15/54, 27.8%), on the basis
of CK5/6 and EGFR expression. Differences in clinico-
pathological characteristics between the basal and non-
basal types are shown Table 3. Biological markers for
the basal and nonbasal types are shown in Table 4. The
basal type was positively correlated with expression of
Ki67 (p = 0.0002), p53 (p = 0.047) and BRCA1(p =
0.03). But the basal type was not correlated with

Clinicopathological Characteristics of Basal Type Breast Cancer in Triple-Negative Breast Cancer
838
Table 2. Antibodies, dilutions, and cutoff value.
Marker Species Manufacturer Dilution Cutoff value
ER Mouse mAb Dako 1:50 >Allred score 3
PgR Mouse mAb Dako 1:100 >Allred score 3
HER2 Rabbit poly Dako 1:250 3+ or FISH+
EGFR Mouse mAb Dako 1:100 >10%
CK5/6 Mouse mAb Dako 1:100 >10%
Ki67 Mouse mAb Dako 1:50 >20%
p53 Mouse mAb Dako 1:50 >10%
SOX2 Rabbit poly MBL 1:100 >10%
BRCA1 Rabbit poly MBL 1:50 >10%
ER, estrogen recepto r; PgR, pr ogest erone recep tor ; HER2, human epider mal
growth receptor-2; EGFR, epidermal growth factor receptor; CK, cy-
tokeratin; BRCA1, breast cancer susceptibility gene I; mAb, monoclonal
antibody; ply, polyclonal antibody; RT, room temperature; FISH, fluores-
cence in situ hybridiza tion.
CK5/6
EGFR
Figure 1. Breast cancer tissues were stained by CK5/6 and
EGFR markers, which were mainly expressed in cytoplas-
mic membrane in tumor cells.
expression of SOX2(p = 0.54). Nonbasal TNBC is more
sensitive to chemotherapy than is the basal type. So far
13 patients had been dead, in other words, the poor
prognosis for basal TNBC is confirmed , which shows
that 12/13 (92.3%) of deaths were diagnosed with the
basal type TNBC (data not shown).
Table 3. Clinicopathological factors according to basal sub-
type in triple-negative cancer.
Basal (n = 39) Nonbasal (n = 15)p value
Age (years),
mean ± SD 58.6 ± 10.5 59.0 ± 9.6 0.91
Menopause
Pre 6 (15.4) 3 (20.0)
Post 33 (84.6) 12 (80.0) 0.69
Tumor size (cm) ,
mean ± SD 3.1 ± 2.2 3.6 ± 2.4 0.48
Nodal status
(–) 21 (53.9) 11 (73.4)
1 - 3 10 (25.6) 2 (13.3)
4~ 8 (20.5) 2 (13.3)
0.41
Stage
Ⅰ 5 (12.8) 4 (26.7)
Ⅱ 13 (66.6) 8 (53.3)
Ⅲ 5 (12.9) 2 (13.3)
Ⅳ 3 (7.7) 1 (6.7)
0.66
Histology
Pap-tub 14 (35.9) 3 (20.0)
Sol-tub 6 (15.4) 5 (33.3)
sci 11 (28.2) 4 (26.7)
Others 8 (20.5) 3 (20.0)
0.47
NG
1 2 (5.1) 1 (6.7)
2 3 (7.7) 1 (6.7)
3 34 (87.2) 13 (86.6)
0.95
ly
(+) 22 (56.4) 8 (53.3)
(–) 17 (43.6) 7 (46.7) 0.84
v
(+) 14 (35.9) 6 (40.0)
(–) 25 (64.1) 9 (60.0) 0.78
Pap-tubl papillotubular carcinoma; Sol-tubl solid-tubular carcinoma; Sci,
scirrhous carcinoma; NG, nuclear grade.

Clinicopathological Characteristics of Basal Type Breast Cancer in Triple-Negative Breast Cancer 839
Table 4. Biological markers according to basal subtype in
triple-negative cancer.
Basal (n = 39), n (%) Non basal (n = 15), n (%) p value
p53
(+) 18 (47.5%) 3 (18.8%) p = 0.047
(–) 21 (52.5%) 12 (81.2%)
Ki67
(+) 29 (72.5%) 3 (18.8%) p = 0.0002
(–) 10 (27.5%) 12 (81.2%)
SOX2
(+) 27 (70.0%) 10 (62.5%) p = 0.54
(–) 12 (30.0%) 5 (37.5%)
BRCA1
(+) 35 (87.5%) 10 (62.5%) p = 0.03
(–) 4 (12.5%) 5 (37.5%)
5. Survival Analysis
Patients with basal type TNBC had significantly shorter
overall survival (p = 0.032) than patients with non-basal
type TNBC (Figure 2).
6. Discussion
Breast cancer is considered to be a heterogeneous group
of tumors showing different behaviors, prognoses and
responses to treatment. Although TNBCs demonstrate
similarities in term of pathological, molecular and cli-
nical characteristics, they do not represent a uniform
clinical entity [6]. Despite its relatively small proportion
among all breast cancers, TNBC is responsible for a
large proportion of breast cancer deaths, due to its
generally aggressive clinical course. But medullary and
apocrine carcinomas have a better prognosis [7]. We
therefore thought it important to classify basal and
nonbasal types in order to resolve this discrepancy.
We demonstrated that the basal type was associated
with a high Ki67 labeling index (p = 0.0002) and, -p53
expression (p = 0.047). The high Ki67 labeling index is
related to the mitotic index and high levels of cell
proliferation. p53 is part of a cell cycle checkpoint,
exhibiting a molecular response to DNA damage re-
sulting in apoptosis [8]. In several studies [9-11] based
on gene as well as protein expression analysis, p53 was
fond to be mutated in up to 82% of basal-type TNBCs.
On the basis of a suggested link to BRCA1 [12], we
investigated the expression of BRCA1. BRCA1 expres-
sion was statistically significant difference in its ex-
pression between basal and nonbasal types (p = 0.03).
Several studies [13,14] have shown that the basal type
Figure 2. Overall survival according to expression of basal
markers (CK5/6 and/or EGFR) in triple-negative breast
cancer. There are statistically significant between basal type
and nonbasal type (p = 0.032).
is associated with tumor size and nuclear grade; however,
the difference of only nuclear grade, was observed be-
tween basal and nonbasal types in this study.
Chemotherapy remains the only systemic treatment
option available for patients with TNBC. Pathological
response to neoadjuvant treatment is very important be-
cause the prognosis is good for patients who achieve a
pathological Complete Response, but extremely poor for
those who do not. In a neoadjuvant study of, 255 patients
with triple-negative disease receiving anthracycline and
taxane-based regimens, Liedtke et al. [15] showed that
the pathological complete response rate for TNBC was
significantly higher than that identified for non TNBC
(22% versus 11%, p = 0.034). There was no significant
correlation between chemotherapeutic regimen and re-
ceptor subtype. Anthracycline and taxane regimens were
used as neoadjuvant chemotherapy in this study as, there
were no other approved drugs. The complete response
rates of the basal and nonbasal types were 12.5% and,
25%, respectively, in this study (data not shown). One of
the reasons is that almost advanced cases in this neo-
adjuvant chemotherapy. A recent study of 4000 cases
compared the prognostic significance of TNBC phe-
notype with and without the addition of EGFR and,
CK5/6. It was shown that the poor prognosis of the
TNBC phenotype was conferred almost entirely by
tumors positive for basal markers [16,17].
Tumors with defective DNA repair pathways, such as
those displaying a BRCA1 deficiency, may be highly
sensitive to DNA damaging agents such as platinum-
based drugs. In a recent neoadjuvant trial of women with
BRCA1 mutations and TNBC, almost 90% of patients
had complete pathological responses to single agent
cisplatin [18]. Results of a recent randomized phase Ⅱ
study of the PARP (Poly (ADP-ribose) polymerase)
inhibitor BSI-201 in combination with carboplatin and
gemcitabine for metastatic TNBC, showed a significantly
improved clinical benefit rate and, progression-free sur-

Clinicopathological Characteristics of Basal Type Breast Cancer in Triple-Negative Breast Cancer
840
vival [19-21]. The development of targeted agents is,
therefore, urgently needed for patients with TNBC.
However, their application to routine clinical practice
remains a long-term goal. In conclusion, our results
indicate that is very important to classify TNBCs into
basal and nonbasal types as basal- type TNBC has a sig-
nificantly worse prognosis and treatment regimen must
be selected accordingly.
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