A 42-year-old woman presented with a mass in the lower inner quadrant of the left breast that had been present for about 1 month. The mass was irregular in shape and rubbery in consistency, and measured 2×1.5 ㎝. It appeared well-demarcated, with
a
high density mass shadow on the mammogram. Lumpectomy was performed, with a 2 ㎝ safety margin surrounding the tumor mass, with simultaneous ipsilateral axillary dissection. The tumor was diagnosed from its histology and immunohistochemistry as a
myoepithelial carcinoma, in which the tumor cells were immunoreactive for the epithelial membrane antigen (EMA), smooth muscle actin and S-100 protein. These proteins are not specific to myoepithelial cells, but in combination, positive findings
indicate myoepithelial differentiation. Most myoepithelial tumors of the breast are benign. However, invasive breast tumors, showing myoepithelial cell differentiation, are rare and usually give rise to metastases. She had received postoperative
radiotherapy, and local recurrence and distant metastasis have not occurred so far. Here, we present a case of myoepithelial carcinoma of the breast, with a review of the literatures.
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