Cytokeratin 7 and 20 expression in
Scott D. Humble, Victor G. Prieto
and Marcelo G. Horenstein
Departments of Pathology, University of South
Alabama Medical Center, Mobile, Alabama,
and University of Texas MD Anderson Cancer
Center, Houston, Texas
Marcelo G. Horenstein MD, Director of
Dermatopathology, University of South Alabama,
2451 Fillingim St, Mobile, AL 36617, USA
Accepted October 3, 2002
Background: Epithelioid sarcoma (ES) is a rare malignant soft tissue
tumor of uncertain histogenesis that arises predominantly in the
extremities of young adults. Immunohistochemically, the neoplastic
cells are typically positive for vimentin, low molecular weight
cytokeratin (CAM5.2) and epithelial membrane antigen (EMA).
Method: We examined eight cases of ES from seven different
patients. All cases were studied with immunohistochemistry for EMA,
CAM5.2 (keratin 8 and 18), 34BE12 (keratins 1, 5, 10 and 14/15),
cytokeratins 7 and 20 (CK7, CK20), and CD34.
Results: The average patient age was 53 (range 43–76) and the
male:female ratio was 5:2. The location was the upper extremity in
five tumors, the lower extremity, the perineum, and the paraspinal soft
tissue in one tumor each. All cases contained predominantly
epithelioid cells, but spindle cells were also present in three cases. All
cases contained areas of geographic necrosis. CAM5.2 was strongly
positive in seven tumors and focally positive in one (8/8). EMA was
diffusely positive in two cases and focally positive in five cases (7/8).
CD34 was diffusely positive in 3/8 cases. 34BE12 was diffusely
positive in one case and focally positive in two others (3/8). CK7 was
diffusely positive in one case and focally positive in another (2/8).
CK20 was negative in all cases (0/8). All cases tested were positive for
vimentin (6/6), 2 cases were focally positive for HHF35 (2/5), and all
cases tested were negative for S-100 protein (0/7).
Conclusions: In addition to the known immunoreactivity for
CAM5.2 and EMA, there is positivity for CK7 and 34BE12 in a small
proportion of cases. None of the cases expressed CK20. This
immunophenotypic profile suggests that ES is more similar to
carcinoma and synovial sarcoma than to other soft tissue tumors, and
may be of diagnostic utility.
Humble SD, Prieto VG, Horenstein MG. Cytokeratin 7 and 20 expression
in epithelioid sarcoma.
J Cutan Pathol 2003; 30: 242–246. # Blackwell Munksgaard 2003.
Epitheliod sarcoma (ES) is a rare, malignant soft tissue
tumor that typically arises in the extremities of young
adults. Although the tumor initially behaves indo-
lently, local recurrences and distant metastases are
frequent.1The histogenesis of ES has been the subject
of controversy. A mesenchymal origin was favored
initially due to association with tendons and fascial
structures, as well as the deep origin of some tumors
within the soft tissue.1Fibroblasts and fixed tissue
histiocytes have been considered as probable progeni-
tor cells; however, a synovioblastic origin has also
been proposed.2,3Ultrastructurally, ES has been
origin.2–4The differential diagnosis of ES is extensive,
as the tumor can be misinterpreted pathologically as
J Cutan Pathol 2003: 30: 242–246
Blackwell Munksgaard. Printed in Denmark
Copyright # Blackwell Munksgaard 2003
nodule, and necrobiosis lipoidica. In addition ES can
be confused with other malignancies, such as meta-
static carcinoma, melanoma, synovial sarcoma, clear
cell sarcoma, epithelioid malignant peripheral nerve
sheath tumor, and epithelioid angiosarcoma.5In most
of these situations, immunohistochemical studies are
necessary to achieve a correct diagnosis. ES usually
molecular-weight cytokeratins; and variably expresses
desmin.6Cytokeratin expression is important because
it distinguishes ES from other sarcomas; however, it
may not set ES apart form metastatic carcinoma or
synovial sarcoma. In this setting, cytokeratin subtyp-
ingmay be helpful.In a largestudyof112 cases of ES,
Miettinen et al.7showed 48% positivity for high-
molecular-weight cytokeratin (34BEH12), 96% positiv-
ity for CK8 (CAM5.2), and 22% positivity for CK7.
However, more recent study by Chu et al.8of CK7
as well as CK20 in ES has cited no reactivity for
either. Most recently, Shiratsuchi et al.9have studied
cytokeratin expression in nine cases of classical ES in a
comparative study with malignant rhabdoid tumor.
These authors found reactivity for CK7 in two ES
cases and lack of CD20 reactivity in all ES cases.
Here, we have examined a group of eight ES to
evaluate expression of cytokeratin subtypes, especially
CK7 and CK20, to validate prior literature and deter-
mine if they have any diagnostic value.
Materials and methods
We examined eight ES from seven different patients.
Five of these tumors were from the files at the Uni-
versity of South Alabama, and three cases were from
the files at University of Texas MD Anderson Cancer
Center. The hematoxylin and eosin stained sections
of formalin-fixed paraffin-embedded tissue were
reviewed for all cases. Immunohistochemistry was
performed in all cases. Immunoreactivity for CK7,
CK20, S-100 protein, epithelial membrane antigen,
muscle-specific actin, vimentin, desmin, and 34BE12
was examined using monoclonal antibodies at dilu-
tions provided by the manufacturer (DAKO Corp.,
Carpinteria, CA). Monoclonal antibody (CAM 5.2)
against cytokeratins 8 and 18 was diluted to the
manufacturer’s (Becton Dickinson, San Jose, CA) dilu-
tion of 1:50. CD34 expression was evaluated using a
monoclonal antibody at a dilution of 1:20 (Becton
Dickenson). The DAKO LSAB2 (labeled streptavi-
din–biotin) system with peroxidase (DAKO Corp.)
was utilized for all antibodies. Immunohistochemistry
for LMW CK, HMW CK, CK7, CK20, CD34 and
EMA wasperformedinall cases. Inaddition, apropor-
tion of cases were analyzed for S-100 protein, desmin,
vimentin, and muscle-specific actin expression.
The age of the seven patients ranged from 43 to
76years (mean 53) at diagnosis, with a male to female
ratio of 5:2 (Table1). Five tumors occurred in the
distal upper extremity, including one recurrent
tumor (case 1a,b) and another (case 2) in whom
diagnosis. The three remaining tumors occurred in the
popliteal fossa, perineum, and paraspinal tissue. All
tumors were treated by wide surgical excision except
for two cases (cases 1, 6) treated by distal upper
extremity amputation and the paraspinal tumor
(case 3), treated by palliative excision. The size of
the tumors ranged from 2.0 to 7.5cm in greatest
dimension. Two patients received radiation therapy
and one received chemotherapy postoperatively.
Metastases and subsequent death occurred in three
patients, with survival from primary diagnosis ranging
from one to 32months. Four patients are alive with-
out disease with a follow-up of 2–42months.
The histologic features of all cases were typical of
ES and consisted of collections of polygonal to
spindled eosinophilic tumor cells surrounding areas
of geographic necrosis (Fig.1). The primary tumor
cell morphology was epithelioid in four tumors,
spindled in one, and a mixture in two tumors
(Fig.2). The immunohistochemical results are sum-
marized in Table1. Seven tumors were positive either
focally (5/8) or diffusely (2/8) for EMA. Diffuse
expression of low-molecular-weight cytokeratin (cyto-
keratins 8 and 18 as recognized by the CAM5.2
antibody) was present diffusely in seven tumors and
focally in one (8/8) (Fig.3). HMW cytokeratins (cyto-
keratins 1, 4, 10, and 14/15 as recognized by the
34BE12 antibody) were diffusely positive in one case
and focally positive in two others (3/8) (Fig.4). CK7
was diffusely positive in case 2 (>50% of tumor cells)
and focally positive in case 5 (<10% of tumor cells)
(2/8). The histologic appearance of case 2 was rather
typical for classical ES, with epithelioid tumor cells
and areas of geographic necrosis (Fig.5). The pattern
of CK7 expression was strong, cytoplasmic staining in
both cases (Figs.6 and 7). CK20 expression was
negative in all tumors (0/8). CD34 was present diffu-
sely in three cases (3/8). S-100 protein was not
detected in any of the analyzed cases (0/7). Two
cases analyzed for muscle-specific actin expression
were focally positive (2/5). All tumors analyzed for
desmin (0/5) were negative. Vimentin was present in
all the analyzed tumors (6/6).
present at initial
In this study we have examined the cytokeratin
expression in eight cases of ES, with an emphasis on
CK7 and CK20. We found LMWCK expression in
CK7 and CK20 in epithelioid sarcoma
all tumors, HMWCK expression in 38% of the
tumors, and CK7 expression in 25% of tumors.
CK20 was notably absent from all cases in our series.
Our overall findings are in agreement with the results
of Miettenen et al.,7who studied 112 ES cases and
found 94% positivity for LMWCK, 48% positivity for
HMWCK, and 22% positivity for CK7. In another
study, Chu et al.8reported no expression of either
CK7 or CK20 in a group of 12 ES. More recently,
Shiratsuchi et al.9have found reactivity for CK7 in
22% of nine classical ES cases and lack of CD20
reactivity in all ES cases. Despite the small number
of cases in our study, we confirm the presence of
CK7 in a minority of ES, in accordance with Miettinen
et al. and Shiratsuchi et al. and the lack of
expression of CK20, in concordance with Chu et al.
and Shiratsuchi et al.7In this manner, our study
dispels some inconsistencies regarding the expression
Table1. Clinical and histopathologic features
CaseA/G LocationSize LMWHMWCK7 CK20RxF/U
LMW, low-molecular-weight cytokeratin; CK7, cytokeratin 7; HMW, high-molecular-weight cytokeratin; CK20, cytokeratin 20; M, male; F, female; Neg,
negative; Ex, excision; Amp, amputation; C, chemotherapy; R, radiation therapy; DOD, dead of disease; A, alive; NED, no evidence of disease.
Fig.1. Typical features of polygonal tumor cells with abundant
cytoplasm surrounding geographic necrosis (case 4, hematoxylin and
Fig.2. Spindled areas were prominent in some cases (case 1b,
hematoxylin and eosin, ?9)
Fig.3. Typical diffuse labeling for low-molecular-weight cytokeratin
as recognized by CAM 5.2 antibody (case 2, immunohistochemistry,
Fig.4. Focal labeling for high-molecular-weight cytokeratin by
34BE12 antibody (case 6, immunohistochemistry, ?22.5)
Humble et al.
of CK7 and reaffirms the lack of expression of
CK7 and CK20 expression by various epithelial
neoplasms has gained recent interest.8Most studies
reveal CK7 expression in a wide variety of carcino-
mas, as opposed to CK20 expression, which is more
limited.10Frequently, metastatic carcinoma enters
the differential diagnosis of ES; hence the findings
regarding CK7 and CK20 expression in ES have
diagnostic implications. The presence of CK7 in a
minority of ES may not help distinguish them from
breast carcinoma, cervical carcinoma, neuroendo-
crine carcinoma, small cell lung carcinoma, salivary
gland tumors, thyroid tumors, endometrial carci-
noma, and synovial sarcoma, all of which usually
express CK7.8On the other hand, expression of
CK20 in a tumor can possibly exclude the diagnosis
of ES and favor the alternatives of colorectal carci-
noma, Merkel cell carcinoma, pancreatic carcinoma,
gastric carcinoma, transitional cell carcinoma, and
cholangiocarcinoma.8The majority of ES are CK7-
and CK20-negative, a pattern which is shared with
prostate carcinoma, squamous cell lung carcinoma,
adrenal cortical carcinoma, germ cell tumors, renal
cell carcinoma, and synovial sarcoma.8
The cytokeratin expression pattern in ES places it
closer to synovial sarcoma than to other sarcomas. A
recent study of keratin expression in the three sub-
types of synovial sarcoma has shown CK7 expression
in nearly 100% of biphasic tumors and 50% of poorly
differentiated tumors. CK20 expression was 27% in
biphasic tumors and 0% in poorly differentiated
tumors.11These cytokeratin studies support a possible
histogenetic similarity between synovial sarcoma
(especially the poorly differentiated variants) and ES,
and emphasize the difficult differential diagnosis
between the two. Further suggestive of a synovial
origin is the finding of a percentage of ES positive
for CK7. CK7 has been reported to be positive in the
glandular component of synovial sarcoma and in
morphologically observable areas of epithelial differ-
entiation (squamoid cells, whorl-like formations)
restricted to synovial sarcoma among spindle cell
sarcomas.12Additional information linking ES and
synovial sarcoma has been recently provided by a
study that analyzed keratin 1 expression, reporting
70% (26/37) in epithelioid sarcomas and 28%
(19/68) in synovial sarcomas.13
In summary, our data show CK7 expression in a
minority of ES and lack of CK20 expression in ES.
The diagnostic utility of CK7 is dubious when analyz-
ing ES, as its presence may not help differentiate ES
from metastatic carcinoma. On the contrary, a tumor
positive for CK20 may help exclude the diagnosis
of ES. The cytokeratin immunophenotypic profile
confirms that ES is more similar to carcinoma and
synovial sarcoma than to other soft tissue tumors.
Part of this work was accepted for presentation at The American
Society of Dermatopathology 38th Annual Meeting, Chicago,
Illinois, September, 2001.
Fig.5. Histologic appearance of case diffusely positive for CK7, had
rather typical epithelioid appearance with areas of geographic
necrosis (case 2, hematoxylin and eosin,?7)
Fig.6. Diffuse labeling for CK7 (case 2, immunohistochemistry, ?9).
Fig. 7. Focal cytoplasmic labeling for CK7 (case 5,
CK7 and CK20 in epithelioid sarcoma
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