P63 Expression in Breast Cancer
A Highly Sensitive and Specific Marker of
Metaplastic Carcinoma
Meryem M. Koker, MD and Celina G. Kleer, MD
(Am J Surg Pathol 2004；28：1506 – 1512)
Abstract
• p63, a member of the p53 gene family, is involved in
cellular differentiation and is expressed in the nuclei of
myoepithelial cells of normal breast.
• In this study, we determined p63 expression in a large
number of breast carcinoma, including metaplastic
carcinoma, and in Phyllodes tumors and sarcoma.
• 189 invasive breast carcinomas, including 15
metaplastic carcinomas, as well as 10 Phyllodes
tumors, and 5 pure sarcoma of the breast for pattern
and intensity of p63 staining using an anti-p63 antibody
(clone 4A4, Neomarkers)
• p63 is strongly expressed in 13 of 15 metaplastic
carcinoma (86.7%).
• p63 is positive in all the metaplastic carcinoma with
spindle cell and/or squamous differentiation (12 od 12).
• Only 1 of 174 (0.6%) nonmetaplastic invasive
carcinomas was positive for p63.
• All Phyllodes tumors and sarcomas were consistently
negative for p63 expression.
• The sensitivity and specificity of p63 as a diagnostic
marker for metaplastic carcinoma was 86.7% and 99.4%
• p63 as part of the diagnostic workup of challenging
spindle cell tumors of the breast as a highly specific
marker for metaplastic carcinomas.
前言：
• Metaplastic carcinoma of the breast (MCB) are a rare
and heterogeneous group of tumors defined by a
cellular component with an appearance other then
epithelial and glandular.
• These tumors may be biphasic and contain glandular
elements mixed with a nonglandular component.
• The majority of metaplastic carcinoma exhibit spindle
cell with or without squamous differentiation.
• The spindle cell component of metaplsic carcinoma
from low-grade “fibromatosis-like” lesions to high
grade spindle cell malignancies resembling
fibrosarcoma or malignant fibrous histiocytoma.
• The diagnosis of metaplastic carcinoma is
straightforward when a direct transition from glandular
epithelial to metaplastic elements is evident, but it
becomes a diagnostic challenge when the neoplasm is
entirely composed of spindle cells.
• p63 is located on chromosome 3q27. Its gene product
is crucial for maintenance of a stem cell population in
several epithelial tissue and is necessary for the
normal development of the epithelial organs including
mammary glands.
• p63 is also expressed in the nuclei of myoepithelial
cells of normal breast ducts and lobules.
• Recently, p63 and other myoepithelial cell markers
have been described in matrix-producing and
metaplastic carcinomas of the breast, suggesting that
these tumors share a myoepithelial cell differentiation.
• Given the specificity of p63 for myoepithelial cells in
the breast and the possible myoepithelial differentiation
of spindle cell metaplastic carcinoma, we postulated
that p63 would be a good marker to distinguish spindle
cell metaplastic carcinoma from other mesenchymal
neoplasm.
• Characterize the expression of p63 in a large group of
invasive carcinomas of different histologic types,
sarcomas, and Phyllodes tumors of the breast define its
diagnostic utility.
Materials and MethodsCase Selection,
Pathologic Evaluation and Immunohistochemistry
• A total of 201 breast tumors were identified by a
retrospective search through the surgical pathology files
at the University of Michigan, comprising 189 invasive
carcinomas, including 15 metaplastic carcinomas. Ten
Phyllodes tumors and 5 primary breast sarcomas were
also retrieved.
• MCB , the architectural pattern and the presence of
epithelial and or heterologous elements were noted.
• The MCB were graded on the basis of the sarcomatoid
component as low-, intermediate-, or high-grade
following described criteria.
• In all cases, the diagnosis of MCB was confirmed by
positive cytokeratin staining including a cytokeratin
cocktail (AE1/AE3, CAM5.2) and/or a high molecular
weight cytokeratin stain (34ßE12)
• A subset of the nonmetaplastic invasive carcioma (160
cases) was arrayed in a high-density tissue microarray.
• At least three tissue core (0.6 mm diameter) were
sampled from different areas of each tumor to account
for tumor heterogeneity using an automated arrayer
(Beecher Instruments).
• Immunohistochemistry using an anti-p63 polyclonal
antibody was performed on the whole tissue sections
and on the tissue microarray simultaneously using
standard biotin-avidin complex technique.
• The p63 antibody (clone 4A4, NeoMarkers, Fremont, CA)
was used at a 1:100 dilution, incubated for 15 mins with
citrate buffer at pH 6, and subjected to microwave
antigen-retrieval pretreatment.
• Normal myoepithelial cells around ducts and lobules
served as positive internal controls.
• A tumor was considered positive when 10% of the
neoplastic cells unequivocally expressed p63 in the
nuclei and negative when less than 10% of the
malignant cells stained for p63.
Results
• Histopathologic features
• Of the 189 invasive carcinomas, 159 were ductal, 10 were
lobular, 5 had ductal and lobular features, and 15 were
metaplastic.
• Of the metaplastic carcinomas, 12 tumors had spindle
and/or squamous areas and 3 had cartilage (Fig 1)
• Table 1
• Fig 1
Histologic feature of metaplastic carcinoma.
A, Biphasic metaplastic carcinoma with well-demarcated spindle and
epithelial components.
B, Metaplastic carcinoma with spindle and epitheloid cells
• Fig 1 C, biphasic metaplastic carcinoma with a squamous area that
blends imperceptibly with the surrounding spindle cell elements.
D, metaplastic carcinoma with spindle cells and dense collagenized
stroma, referred to as “keloidal type”
• The low- and intermediate- grade spindle cell MCB
were characterized by elongated, fusiform cells with
minimal to moderate cytologic atypia and rare or no
mitoses. In contrast, the high-grade spindle cell
carcinomas displayed marked pleomorphism,
hyperchromasia, and numerous atypical mitoses.
• The neoplastic cells in both low- and high- grade
spindle cell carcinomas infiltrated adjacent mammary
and adipose tissue and were interrupted by dense
collagen bands.
• p63 Expression in Invasive Carcinomas of the Breast
• p63 was expressed in the nuclei of myoepithelial cells of
normal ducts and lobules adjacent to the carcinomas,
which also served as internal positive controls in all cases
(Fig 2a)
• p63 was not detectably expressed in the luminal cells of
normal structures in any cases. Stromal fibroblasts and
myofibroblasts were consistently negative in all case.
• Tab 2, Fig 2
• Fig 2 A. p63 expression in normal breast and in metaplastic
carcinomas. A, normal terminal-duct lobular unit with p63 expressing
myoepithelial cells, which served as positive internal control.
• Fig 2 B-F, Strong and diffuse expression of p63 in metaplastic
carcinomas with spindle and squamous areas. Note that the staining is
crisp and easily discernible even at low power.
• The single nonmetaplastic carcinoma that was positive
for p63 was a high-grade invasive ductal carcinoma
with no special features; however, the percentage of
positive malignant cells was much lower than in the
metaplastic carcinoma (10% vs mean of 70%)
• p63 was negative in all the other invasive ductal,
lobular and mixed ductal and lobular carcinoma.
• p63 Expression in Mesenchymal tumors of the Breast
• p63 was consistently negative in the spindle and
epithelial cell components of all benign and malignant
Phyllodes tumors
• Fig 3
• The sensitivity and specificity of p63 as a marker for
metaplastic carcinoma is 86.7% and 99.4%, respectively,
with a 100% specificity for MCB with spindle cell and/or
squamous areas.
• Fig 3 A and B P63 is not expressed in Phyllodes tumors and
sarcomas of the breast. A and B. Phyllodes tumor
• Fig 3.C and D Note that p63 is only expressed in the normal
myoepithelial cells associated with the epithelial component. The
spindle cells are negative. C and D, Primary osteosarcoma of the
breast, negative for p63
Discussion
• Traditional, MCB has been defined as a malignant tumor
•
•
in which part of all of the carcinomatous epithelium is
transformed into a nonglandular (metaplastic) growth
process.
The most common metaplastic components are spindle
cell and squamous, wereas heterologous elements
including osseous, chondroid, and other sarcomas
comprise a minority of tumors.
MCB with a prominent spindle cell component display
histologic patterns ranging from those resembling
highly pleomorphic and anaplastic sarcomas to bland
benign-appearing lesions.
• To data, the best mechanism other than morphologic
examination for differentiating MCB from these other
spindle cell tumors has been cytokeratin staining.
• Several studies hae shown that staining with a broadspectrum anti-CK antibody or high molecular weight CK
(34ßE12) provides the most sensitive marker for MCB.
• Other markers, such as smooth muscle actin, CK5, CK14,
CAM5.2, and AE1/AE3, have also been examined for their
utility in the diagnosis of MCB, but more than half of the
cases were negative for any one of these antibodies.
• Importantly, CK-positive metaplastic carcinomas, even
those stained with 34ßE12 or broad-spectrum CKs,
often only show focal or patchy positive, particular in
small core biopsies, leading to potential misdiagnoses.
• Apart from the CK stains, CD34, smooth muscle actin,
vimentin, and occasionally Bcl-2 have been proposed
as helpful adjuncts when the differential diagnosis
includes MCB, sarcoma of the breast, and Phyllodes
tumor.
• However, borderline and malignant Phyllodes tumors,
the types most likely to cause diagnostic confusion
with metaplastic carcinomas, are much less likely to be
positive for any of these markers.
• All the MCB with spindle cell and squamous
components stained strongly for p63 in the nuclei,
which confirms previous reports.
• Surprisingly, we found that only 1 of the 174
nonmetaplastic invasive carcinoma (0.6%) was positive
for p63 expression, and the percentage of positive cells
in this carcinoma was much smaller then in the MCB
(10% vs. a mean of 70% for MCB)
• This tumor was an invasive ductal carcinoma, with high
histologic grade and no special features.
• While all the of metaplastic spindle cell carcinomas
stained strongly with p63, none of the Phyllodes
tumors or primary breast sarcomas showed any p63
expressed.
• Emerging data suggest that the metaplastic component
and the adenocarcinoma have a clonal origin.
• It has been suggested that these tumors arise from a
single stem cell, a group of different cells, or a
common progenitor cell capable of differentiating into
other cell types.
• Using laser capture microdissection of a tumor with
carcinomatous and sarcomatoid component, Wada et
al found that both areas had identical patterns of Xchromosome inactivation and the same of p53
mutation, strongly supporting the hypothesis that this
tumor is derived from a single totipotent stem cell.
• Furthermore, the concept that the metaplastic spindle
elements have myoepithelial differentiation is
supported by the present study and by several studies
showing that these cells are reactive for myoepithelial
markers, including high molecular weight CK, p63, and
maspin.
• In summary, p63 is a specific and sensitive marker for
MCB, and particularly specific for metaplastic
carcinomas with spindle and/or squamous areas
• It is a highly complementary stain to CK because p63 is
a nuclear marker, which has a strong and diffuse
staining pattern that is easily discernible, even at low
power.
• We propose the inclusion of p63 in the diagnostic
workup of challenging spindle cell tumors of the breast.