British Journal of Radiology (2005) 78, 444-446
© 2005 British Institute of Radiology
doi: 10.1259/bjr/73238635
Myoepithelial carcinoma of the breast: a case report with imaging and pathological findings
E K Woo, MRCP (UK)1,
A D James, FRCS2,
J Mercer, MRCPath3,
S M Allan, FRCS2 and
D C Howlett, MRCP (UK), FRCR1
Departments of 1 Radiology, 2 Breast Surgery and 3 Histopathology, Eastbourne District General Hospital, Kings Drive, Eastbourne, East Sussex BN21 2UD, UK
Correspondence: Dr David Howlett, Consultant Radiologist
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Abstract
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We present a case of myoepithelial carcinoma of the breast together with illustrations of the imaging and pathological appearances as well as discussion on the management of this condition.
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Introduction
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Adenomyoepithelioma of the breast is an unusual benign tumour characterized by biphasic proliferation of epithelial and myoepithelial cells. Malignant change is extremely rare and may involve both cellular components – myoepithelial carcinoma. We present a case of myoepithelial carcinoma together with illustrations of the imaging and pathological appearances as well as discussion on the management of this condition.
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Case report
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A 70-year-old female presented with a recent onset of a painless left-sided breast lump. Clinical examination revealed a firm mass in the outer lower quadrant with no axillary lymphadenopathy palpable. A mammogram was performed. This was technically difficult owing to the patient's immobility and only a lateral oblique view was feasible. This showed an ill-defined mass in the inferior aspect of the left breast (Figure 1
). Subsequent ultrasound examination demonstrated a rounded, hypoechoic solid lesion with the margins ill-defined in part suspicious of malignancy (Figure 2). Fine needle aspiration was performed which confirmed malignant cytology. Chest radiograph and liver ultrasound did not show any evidence of metastatic disease. The patient had a significant history of coronary heart disease and therefore a decision was made to excise the lesion under local anaesthesia.
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Figure 1. Lateral oblique mammogram of the left breast. An ill-defined opacity is seen inferiorly (arrow).
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Figure 2. Left breast ultrasound shows a rounded, hypoechoic solid lesion with the borders ill-defined in part.
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Histology showed a 15 mm x 15 mm x 10 mm well-circumscribed solid mass, which appeared pale on slicing with a central area of necrosis. It consisted of islands and tubular structures composed of epitheloid cells surrounded by a fibrous stroma. Many of the epitheloid cells had clear cytoplasm. They had moderately pleomorphic nuclei and a high mitotic rate. At the periphery of the lesion there were strands of epitheloid cells, which appeared to infiltrate the stroma (Figure 3). Immunocytochemical staining showed strong positive staining for S100 protein (Figure 4). There was positive staining for cellular adhesion molecule (CAM 5.2) and for other individual cytokeratins. These appearances were diagnostic for myoepithelial carcinoma.
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Figure 3. Haematoxylin and eosin high power view of the tumour margin showing infiltration of the stroma and mitosis (arrow).
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Discussion
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Adenomyoepithelioma of the breast is an unusual benign tumour, first described in 1970 [1] and is characterized by biphasic proliferation of epithelial and myoepithelial cellular constituents. Recent reports have indicated that one or both of the cellular constituents may undergo malignant change, myoepithelial carcinoma, although this is extremely rare [2–6]. Metastases from myoepithelial carcinoma are described and appear to be haematogenous rather than lymphatic and they also appear to be restricted to primary tumours greater than 2 cm [7–12]. These tumours are prone to local recurrence as is adenomyoepithelioma and can be predicted by narrow or incomplete excision margins [6].
Clinically, myoepithelial carcinoma presents as a rapidly enlarging mass, which may be tender and is often laterally placed in the breast [3].
The imaging findings of myoepithelial carcinoma do appear to be non-specific [2]. In our patient, as in previous cases, both mammography and ultrasound showed features suspicious for malignancy confirmed on cytology. Myoepithelial carcinoma may be difficult to diagnose specifically cytologically and core biopsy may be more accurate.
Histologically, the myoepithelial cells frequently have clear cytoplasm and immunohistochemically typically stain for S100, CAM5.2 and other cytokeratins. Malignant transformation of the cellular components indicates a carcinoma. Currently, surgical management of this rare malignant tumour is similar to that for other breast malignancy namely wide local excision or mastectomy with axillary surgery if appropriate. The response to chemotherapy and radiotherapy is unknown. If following wide local excision, the excision margin is narrow or incomplete, re-excision is advised to gain adequate margins.
In conclusion, myoepithelial carcinoma is a rare tumour, which should be considered in the differential diagnosis of a solid breast lesion. The imaging findings appear to be non-specific reflecting the malignant nature of the tumour. Surgeons and radiologists should be aware of its potential for local recurrence following wide local excision and the possibility of haematogenous rather than lymphatic metastases.
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Acknowledgments
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The authors would like to thank Nick Taylor for preparing the illustrations.
Received for publication September 6, 2004.
Accepted for publication January 17, 2005.
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References
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Abstract
Introduction
