Breast adenomyoepithelioma: a case report with malignant proliferation of epithelial and myoepithelial elements

Abstract

Background: Breast adenomyoepithelioma is an unusual tumor characterized by a biphasic proliferation of epithelial and myoepithelial cells. Most breast adenomyoepitheliomas are considered to be benign or to have a low-grade malignant potential, characterized by propensity for local recurrence. Malignant changes arising in this lesion are extremely rare and may involve one or both cellular components.

Case report: We discuss a case of a 60 year-old woman who began to experience pain in her right breast in January 2009. Breast ultrasound and mammography were performed showing a rounded, hypoechoic solid lesion with ill-defined margins in the right inner-inferior quadrant, suspicious of malignancy. Quadrantectomy of the inner-inferior quadrant of the right breast with sampling of ipsilateral axillary lymph nodes was performed. The histological analysis confirmed the diagnosis of adenomyoepithelioma with focal malignant change of the epithelial component, associated with high-grade malignant myoepithelial change. The patient was treated with adjuvant radiotherapy and her right breast received a dose of Gy 50 with a boost of Gy 10 to the tumor bed. At present, the patient shows no sign of tumor recurrence.

Conclusion: Breast malignant adenomyoepithelioma is a rare tumor which should be considered in the differential diagnosis of other solid breast lesions. Only few cases have been reported in the literature. Diagnosis, optimal therapy and predicting the outcome are problematic issues due to the rarity of this disease which appears to have hematogenous rather than lymphatic spread and usually occurs in primary tumors ≥ 1.6 cm in size.

Figure 1

Radiological characteristics of lesion; (A and B) mammography craniocaudal and mediolateral oblique views of the right breast show an ill-defined end opacity in the inner-inferior quadrant of about 20 mm diameter; (C): ultrasonography of the right breast shows a hypoechoic nodule of about 17 mm diameter around the right mammary region near the areola.

Figure 2

Morphological characteristics of the lesion; (A) the lesion shows multilobulated outlines and pushing margins (hematoxylin-eosin, magnification 4×); (B) the benign component is composed of rounded or elongated tubules lined by a single layer of epithelial cells and one or two layers of myoepithelial cells (hematoxylin-eosin, magnification 40); (C) the malignant component shows cytological atypia of epithelial and myoepithelial components (hematoxylin-eosin, magnification 40×).

Figure 3

Immunohistochemical characteristics of the lesion; (A) expression of CK 7 (magnification 10×); (B) expression of p63 (magnification 10×); (C) expression of CK 5 (magnification 10×); (D) expression of S-100 (magnification 10×).