AJR 2003; 180:799-803
© American Roentgen Ray Society
Adenomyoepithelioma of the Breast: Spectrum of Disease with Associated Imaging and Pathology
D. C. Howlett1,
C. H. Mason2,
S. Biswas3,
P. D. Sangle3,
G. Rubin1 and
S. M. Allan3
1 Department of Radiology, Eastbourne District General Hospital, Kings Dr.,
Eastbourne, East Sussex BN21 2UD, United Kingdom.
2 Department of Histopathology, Eastbourne District General Hospital, East
Sussex BN21 2UD, United Kingdom.
3 Department of Breast Surgery, Eastbourne District General Hospital, East
Sussex BN21 2UD, United Kingdom.
Received June 24, 2002;
accepted after revision August 7, 2002.
Address correspondence to D. C. Howlett.
Abstract
OBJECTIVE. Our objective was to show the spectrum of biologic
behavior associated with breast adenomyoepithelioma. This disease is a rare
benign breast neoplasm characterized by proliferation of both epithelial and
myoepithelial cellular elements. Malignant change of one or both cell types
may occur and is thought to be associated with hematogenous, rather than
lymphatic, metastasis.
CONCLUSION. Three patients with benign and malignant
adenomyoepithelioma were included in this study. The imaging and
histopathologic findings in these three patients are illustrated, and the
treatment of patients with this unusual tumor is discussed.
Introduction
Adenomyoepithelioma of the breast is a rare tumor characterized by biphasic
proliferation of both epithelial and myoepithelial cells. Most tumors are
benign, but malignant degeneration, although unusual, may occur. In this
article, three patients with breast adenomyoepithelioma are presented with
imaging and pathologic findings that illustrate the range of biologic behavior
associated with this neoplasm.
Materials and Methods
The study comprised three women (age range, 69-74 years) who presented over
a 1-year period with unilateral breast lesions. The first patient was
asymptomatic and was referred for further investigation with a screen-detected
abnormality. The remaining two patients presented with recent onset of
palpable, enlarging, and nontender breast lumps lying centrally above the
nipple. Clinical examination was otherwise unremarkable, with no evidence of
associated lymphadenopathy. After the clinical evaluation, all patients
underwent mammography, sonography, and fine-needle aspiration biopsy as part
of their further assessment.
Results
In the patient who underwent screening mammography, a small circumscribed
lesion in the outer lower quadrant of her left breast lying 5 cm deep relative
to the nipple was detected (Fig.
1A). Sonography of the left breast confirmed the presence of a
circumscribed and homogeneous solid nodule
(Fig. 1B), and sonographically
guided fine-needle aspiration biopsy of this lesion was undertaken. The
aspirate was highly cellular, and despite the presence of a biphasic pattern
in areas, the aspirate was considered suspicious. Local excision for formal
histologic assessment was therefore advised and showed a completely excised
tubular benign adenomyoepithelioma (Fig.
1C).
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Fig. 1A. —69-year-old woman with benign tubular adenomyoepithelioma.
Lateral oblique mammogram shows circumscribed mass lying inferiorly in left
breast (arrow). Benign calcifications are also present.
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Fig. 1C. —69-year-old woman with benign tubular adenomyoepithelioma.
Photomicrograph of histologic specimen of resected benign adenomyoepithelioma
shows inner layer of epithelial cells (white arrow) and outer layer
of myoepithelial cells (black arrow). (H and E, x100)
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In the second patient, mammography showed a lobulated mass above the left
nipple (Fig. 2A). Sonography
confirmed that this lesion was hypoechoic with an ill-defined margin and was
suspicious for malignancy (Fig.
2B). Sonographically guided fine-needle aspiration biopsy was
undertaken, which revealed malignant cells, and the patient underwent a left
mastectomy and axillary dissection. Histology showed an infiltrating ductal
carcinoma, not otherwise specified, arising in a lobulated benign
adenomyoepithelioma (Fig. 2C)
with no evidence of metastasis in 10 axillary nodes. The findings from the
chest radiograph and the liver sonogram were normal. The patient has remained
well over a 2-year follow-up period with no evidence of tumor recurrence.
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Fig. 2A. —72-year-old woman with infiltrating ductal carcinoma arising
in benign adenomyoepithelioma. Lateral oblique mammogram of left breast shows
lobulated and ill-defined opacity lying just above nipple (arrow). No
associated microcalcifications are evident.
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Fig. 2B. —72-year-old woman with infiltrating ductal carcinoma arising
in benign adenomyoepithelioma. Sonogram of left breast confirms ill-defined
hypoechoic solid mass (calipers) above nipple, suspicious for
malignancy.
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Fig. 2C. —72-year-old woman with infiltrating ductal carcinoma arising
in benign adenomyoepithelioma. Photomicrograph of resected specimen shows
infiltrating ductal carcinoma (not otherwise specified) arising in benign
adenomyoepithelioma. (H and E, x100)
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In the third patient, mammography showed a large lobulated mass with an
ill-defined margin above the right nipple with associated architectural
distortion (Fig. 3A).
Sonography confirmed this lesion to be hypoechoic, ill-defined, and suspicious
for malignancy (Fig. 3B), and
sonographically guided fine-needle aspiration biopsy confirmed malignant
cytology. The patient underwent a right mastectomy and axillary dissection.
Histology revealed an adenomyoepithelioma with malignant degeneration
containing areas of high-grade myoepithelial carcinoma (Figs.
3C,3D,3E,3F).
There was no evidence of metastatic involvement of 12 axillary nodes, and the
findings of the chest radiograph and the liver sonogram were normal. The
patient has remained well with no evidence of tumor recurrence or metastatic
disease over 18 months of follow-up.
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Fig. 3B. —74-year-old woman with myoepithelial carcinoma. Sonogram of
right breast confirms presence of illdefined, hypoechoic, and solid mass with
associated distal acoustic shadowing. Imaging features are suspicious for
malignancy. D1 and D2 indicate caliper measurements.
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Fig. 3C. —74-year-old woman with myoepithelial carcinoma.
Photomicrographs of histologic specimens of benign adenomyoepitheliomatous
elements from tumor in right breast show inner epithelial and outer
myoepithelial cell layers (C) and smooth muscle  -actin stain and
immunoperoxidase technique that stains myoepithelial cell layer
(arrow, D). (H and E, x100)
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Fig. 3D. —74-year-old woman with myoepithelial carcinoma.
Photomicrographs of histologic specimens of benign adenomyoepitheliomatous
elements from tumor in right breast show inner epithelial and outer
myoepithelial cell layers (C) and smooth muscle -actin stain and
immunoperoxidase technique that stains myoepithelial cell layer
(arrow, D). (H and E, x100)
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Fig. 3E. —74-year-old woman with myoepithelial carcinoma.
Photomicrographs of histologic specimens show myoepithelial carcinoma in
adenomyoepithelioma of right breast with spindle cell elements (E) and
epithelioid cell elements (F). (H and E, x200)
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Fig. 3F. —74-year-old woman with myoepithelial carcinoma.
Photomicrographs of histologic specimens show myoepithelial carcinoma in
adenomyoepithelioma of right breast with spindle cell elements (E) and
epithelioid cell elements (F). (H and E, x200)
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Discussion
Adenomyoepithelioma of the breast is a rare tumor that was first described
in 1970 [1]. Most cases have
occurred in women [2].
Adenomyoepithelioma of the breast arises from myoepithelial and epithelial
cells that are widely present in the normal breast lobules and ducts. Similar
tumors derived from myoepithelial cells have been recognized in the salivary
glands for some time [3]. Most
breast adenomyoepitheliomas are benign and are characterized by biphasic
proliferation of epithelial and myoepithelial cellular elements.
The typical histologic appearance of a benign adenomyoepithelioma consists
of acinar structures composed of an inner layer of epithelial cells with
eosinophilic cytoplasm (Figs.
1C,
3C, and
3D) and a prominent peripheral
layer of myoepithelial cells
[4]. The myoepithelial cells
frequently have clear cytoplasm and are readily shown immunohistochemically
via positive staining for smooth muscle -actin (Figs.
3C and
3D), smooth muscle myosin, and
S-100 protein. Adenomyoepitheliomas have been classified as tubular,
lobulated, or spindle cell variants on the basis of their growth pattern
[5]. Combinations of growth
patterns sometimes exist.
Malignant change in an adenomyoepithelioma has been previously reported.
Malignant change may involve only one cellular element, more often the
epithelial component than the myoepithelial component
[4,
6]
(Fig. 2C). Malignant
transformation of both cellular elements may also occur, but it is extremely
rare [7] (Figs.
3E and
3F). The evolution of
malignant adenomyoepithelioma seems to begin with adenosis, with or without
myoepithelial hyperplasia, advances to benign adenomyoepithelioma, and then
proceeds to a possible malignant transformation
[7]. To our knowledge,
malignant change in an adenomyoepithelioma has not yet been described in a
male patient.
Metastases may occur in malignant myoepi-thelioma and can consist of one or
both cellular components [8].
In a review of 12 cases of biphasic malignant adenomyoepithelioma, one study
found that lung metastases were present in three patients and brain metastases
in two [7]. Metastases from
malignant adenomyoepi-thelioma appear to be hematogenous rather than
lymphatic, and no cases of lymphatic involvement were identified in this
series. Metastases appear to be restricted to primary tumors larger than 2 cm
[7]. Metastasis to the thyroid
gland has also been detected in one patient 12 years after the initial
excision of a malignant breast adenomyoepithelioma
[9].
Because of the rarity of adenomyoepithelioma and the varied and
hypercellular nature of these tumors, they can be confused with other
neoplasms cytologically [10].
Core biopsy may potentially provide a more accurate mechanism of diagnosis. If
a benign adenomyoepithelioma is diagnosed after fineneedle aspiration biopsy
or core biopsy, then total excision of the lesion with a margin of uninvolved
breast tissue is recommended.
Both benign and malignant adenomyoepi-theliomas are prone to local
recurrence after excision and may recur several years after the initial
surgery [11]. The best
predictor for local recurrence of a benign adenomyo-epithelioma is an initial
incomplete or narrow excision margin. If the excision margin is narrow or
incomplete, reexcision to gain adequate margins is recommended. Tubular
variants and some lobular tumors with high mitotic activity are particularly
prone to local recurrence [5].
However, in adenomyo-epitheliomas that contain a combination of cell types,
there is no evidence that the relative proportions of individual cell groups
is a risk factor for local recurrence
[4]. If carcinoma (epithelial
or myoepithelial) is diagnosed histologically in an excised
adenomyoepithelioma thought to be benign, then the lesion should be treated as
a carcinoma.
Clinically, adenomyoepithelioma tends to present as a palpable, nontender,
and centrally located mass, although a more peripheral distribution and lesion
tenderness may occur [5]. Rapid
enlargement of a mass is highly suggestive of malignant change. The imaging
features of breast adenomyoepithelioma are not well described. In our patient
with benign adenomyoepithelioma, imaging showed benign features with the
lesion appearing circumscribed and having no associated parenchymal
distortion. In the two patients with malignant adenomyoepithelioma,
mammography and sonography both showed features suspicious for malignancy,
namely poorly defined lesion margins and marked distortion of the surrounding
breast parenchyma, with distal acoustic shadowing apparent on sonography. No
malignant microcalcifications were present. Although these imaging appearances
were not specific, the mammographic and sonographic features were indicative
of the underlying benign or malignant nature of the adenomyoepithelioma.
In conclusion, adenomyoepithelioma is an unusual breast neoplasm and should
be considered in the differential diagnosis for a focal solid lesion in the
breast. Most of these tumors are benign, but malignant change of one or both
cellular components may occur, and larger malignant tumors appear to be
associated with hematogenous metastasis. The imaging features of
adenomyoepithelioma are not well described, but our series reflected the
benign or malignant nature of the underlying tumor. The cytopathologist should
be aware of the occasionally confusing cytologic appearance of
adenomyoepithelioma, and the surgeon and the radiologist also need to be alert
of the potential for recurrence after local excision.
Acknowledgments
We thank Louise Pellett for typing the manuscript and Nick Taylor for
preparing the illustrations.
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Abstract
Introduction
