Summary: A healthy 55-year-old woman presented for her annual screening
mammogram. She had no personal or family history of breast cancer or
heightened risk factors for breast cancer.
Screening mammography revealed a 1-cm focal asymmetry with a very
subtle lobular shape and smooth, microlobulated margin at the
inferomedial quadrant of the left breast, 2 cm from the nipple (Figure
1). No fatty hilus or malignant calcifications were identified.
patient was recalled from screening and additional diagnostic images
and directed sonography confirmed an oval, well-circumscribed solid mass
with smooth borders, and color Doppler flow (Figure 2). An
uncomplicated ultrasound-guided core needle biopsy was completed.
Hemotoxylin-eosin, S100, and MA903 histologic stains identified
myoepithelial nuclear and cytoplasmic elements consistent with
adenomyoepithelioma (Figure 3).
The Breast Imaging Reporting and Data System (BI-RADS) developed by
the American College of Radiology enables the use of consistent language
in the radiology report. The uniform description facilitates
standardized communication between and among breast imagers. Mass shape
(round, oval, lobular, irregular), margin (circumscribed,
microlobulated, indistinct, ill defined, spiculated) and density (high,
equal, low, fat-containing) are defined in BI-RADS.1 This
case illustrates the importance of lesion characterization in a small,
otherwise benign mass. The border lobulation in a
nonaggressive-appearing mass triggered further evaluation. Though the
lesion was small, its shape and margin were accurately identified on
mammography. The sonographic features of uniformly iso- to
hypoechogenic, circumscribed margins with no through transmission and
positive vascularity on color Doppler were consistent with a solid mass.
present the first published case of a lesion containing
adenomyoepithelioma imaged with photon-counting digital mammography.
Photon-counting digital mammography is the most recent fundamental
improvement in mammographic x-ray detector technology. The 50-micron
detector resolution and up to 50% dose reduction are unique to MicroDose
(Philips Healthcare, Andover, MA). The very subtle characteristics of
the mass shape and margin were accurately identified with the
photon-counting mammography system; such subtle features in this case
could easily have been misinterpreted as normal glandular tissue if the
images were of the lower resolution (up to 4 times lower) produced by
standard mammographic systems (personal communication).
is a rare myoepithelial breast lesion, with only 150 cases documented
in the literature. Patients range from 26 to 81 years.2 Most adenomyoepitheliomas are benign and occur in women.3
They do have malignant potential to metastasize hematogenously to the
brain and lungs; however, only 40 of the 150 cases have been identified
as having malignant potential.
The mass may present as a central,
nontender, palpable abnormality or as an incidental finding on screening
mammography. These tumors are characterized by a biphasic proliferation
of epithelial and myoepithelial elements.4 The typical
histologic appearance of benign adenomyoepithelioma consists of acinar
structures, an inner layer of epithelial cells with eosinophilic
cytoplasm, and a peripheral layer of myoepithelial cells.5
The myoepithelial lesions are immunoreactive with dark-brown staining
for alpha-smooth muscle actin, calponin, and myosin. In the case of our
patient, the specimen was positive for S100, a stain for epithelial
cells, and MA903, a stain for keratins on myoepithelial cells. These
markers are indicative of the adenomyoepithelioma histology (Figure 3).
case illustrates the importance of accurate border and margin
evaluation despite initial nonaggressive imaging features in routine
screening mammography. Though the lesion appeared nonaggressive and
lacking a fatty hilus on mammography or sonography, thereby excluding an
intramammary lymph node, tissue diagnosis is imperative to evaluate
other benign, nonaggressive masses. The margins were exquisitely sharp
on photon-counting digital mammography and there were no
microcalcifications. The differential diagnosis as described in the
literature includes fibroadenoma, malignant myoepithelioma, spindle-cell
carcinoma, aggressive fibromatosis, and various other myofibroblastic
lesions (Table 1).6
The lesion margins must be
accurately characterized as circumscribed, indistinct, or spiculated. In
small lesions, subtle features may not be readily apparent on standard
mammography. The nonaggressive lobulated margin is a key feature of
adenomyoepitheliom; nonetheless it is as nonspecific as any other
nonaggressive lesion.5 Variability in these characteristics
is based on the cellular composition of the tumor. In our patient’s
sonogram, the mass was circumscribed with no posterior sonographic
enhancement. There was vascularity on color Doppler (Figure 2). This
lesion is in contrast to typically mammography-malignant lesions, which
have poorly defined margins and architectural distortion.5 As
in our case, surgical excision is recommended even if the diagnosis at
needle biopsy is benign adenomyoepithelioma. Pleomorphism may include
fibroadenoma and malignant adenomyoepithelial elements. There is a risk
of local recurrence several years after the first surgical excision.7
- American College of Radiology. Breast imaging reporting and data system, breast imaging atlas. 4th ed. Reston, VA: American College of Radiology, 2003.
- Park Y, Okuyama N, Hatano Y, et al. Adenomyoepithelioma of the breast: A case report and a review of literature. Breast Cancer. 1996;3:65–69.
- Ruiz-Delgado ML, López-Ruiz JA, Eizaguirre B, et al. Benign
adenomyoepithelioma of the breast: Imaging findings mimicking malignancy
and histopathological features. Acta Radiol. 2007; 48:27-29
- Ahmed AA, Heller DS. Malignant adenomyoepithelioma of the breast
with malignant proliferation of epithelial and myoepithelial elements: A
case report and review of the literature. Arch Pathol Lab Med. 2000;124:632-636.
- Rosen PP. Adenomyoepithelioma of the breast. Hum Pathol. 1987;18:1232-1237.
- Howlett DC, Mason CH, Biswas S, et al. Adenomyoepithelioma of the
breast: Spectrum of disease with associated imaging and pathology. AJR Am J Roentgenol. 2003;180:799-803.
- Loose JH, Patchefsky AS, Hollander IJ, et al. Adenomyoepithelioma of the breast: A spectrum of biologic behavior. Am J Surg Pathol. 1992;16:868-876.