RESUMO
Adenomyoepithelial adenosis of the breast is extremely rare. We treated a 35-year-old woman with two small painless hard lumps in her breasts. On ultrasonography, the lesion in the right breast (upper inner quadrant) showed heterogeneous echogenicity and irregular, well-defined, uniformly hypoechoic nodules separated by funiform hyperechoic areas. The entire lesion had unclear boundaries. Excisional biopsy showed adenomyoepithelial adenosis. The mass in the left breast was a fibroadenoma. Adenomyoepithelial adenosis can show local recurrence and malignant degeneration, therefore, preoperative ultrasonographic diagnosis is important for surgical planning. The differential diagnosis includes common adenosis, fibroadenoma, adenomyoepithelioma and adenomyoepithelial carcinoma.