Background: Epithelial-myoepithelial carcinoma is a very rare carcinoma that both luminal and myoepithelial components are malignant. What’s more, HER2 gene amplification has not been detected in the literature up to now. Herein, we report a rare case of breast epithelial-myoepithelial carcinoma with HER2 gene amplification.
Case presentation: An 80-year-old woman presented with a mass in the upper outside region of her left breast. The core needle biopsy of the left breast mass revealed invasive breast carcinoma, and then modified radical mastectomy of left breast was performed. Macroscopically, the tumor was measured 6cm in diameter, and it was a solid and lobulated mass with areas of cystic and hemorrhagic lesions. Microscopically, the histological findings of tumor were consisted of 3 components. One component showed biphasic proliferation of both eosinophilic luminal epithelial and pale abluminal myoepithelial cells, arranging predominantly in dilated tubular architecture, which accounted for most of the lesion. Papillary architecture and eosinophilic secretions could be seen in some dilated ducts. The second component was proliferation of myoepithelial cells with pale cytoplasm around the glandular epithelium forming casing-like structures. The third component was few solid-appearing areas which was displayed a predominance of monophasic proliferation of myoepithelial cells. Both cell types exhibited enlarged and markedly atypical nuclei, with obvious nucleoli and prominent mitoses (up to 10-15/10 high power fields). Foci of infiltration were identified at the periphery of the lobules and the surrounding adipose tissue. Areas of central necrosis and stromal hyalinization could be seen. A diagnosis of EMC was made by morphology and immunohistochemistry. It's worth noting that HER2 gene amplification has not been detected in malignant adenomyoepitheIioma in the literature up to now; While in our present report, HER2 was 2+ membranous immunoreactivity, and then HER2 gene amplification was detected by fluorescence in situ hybridization.
Conclusion: Accurate diagnosis of malignant adenomyoepitheIioma is challenging but of great importance, and the management of malignant adenomyoepitheIioma would be made according to histologic features.