Breast mucoepidermoid carcinoma: a case report and review of literature

Abstract

Breast mucoepidermoid carcinoma (MEC) is clinically rare, with an estimated incidence of 0.2-0.3% of all primary breast tumors. To date, only 41 cases have been reported in the literature. Herein, we present a case of breast MEC diagnosed at our hospital. The clinicopathologic features were preliminarily discussed by reviewing the literature. A 42-year-old Chinese woman presented with a lump in her right breast that was detected approximately three months prior. A microscopic examination showed that the breast MEC was composed of different proportions of mucinous cells, intermediate cells, and epidermoid cells. Most mucinous cells were positive for cytokeratin 7, while the epidermoid and intermediate cells were positive for p63 and cytokeratin 5/6. All tumor cells were negative for other myoepithelial markers, such as calponin. Tumor cells did not express estrogen, progesterone, or the HER-2/neu protein. After the patient underwent mastectomy, she was diagnosed with a low-grade mucoepidermoid carcinoma based on the clinical, histologic, and immuno-phenotypic characteristics. Our findings provide further insight into the pathologic mechanism of MEC, as correct diagnosis is essential for patient management.

Keywords: Breast; immunohistochemistry; mucoepidermoid carcinoma; pathologic morphology.

Figure 1

Ultrasonography showing a cystic lesion of the right breast.

Figure 2

Histopathologic features of mucoepidermoid carcinoma of the breast. A. The lesions are constituted by solid neoplastic nests and scattered cystic spaces filled with mucoid material; (×100). B. Three cell types were observed in mucoepidermoid carcinoma. Intermediate cells are on the left (red arrow); epidermoid cells are localized centrally (black arrow); (×100). C. AB-PAS stains show numerous mucinous cells in the invasive component (The arrow points to mucoid material); (×100).

Figure 3

Immunohistochemistry of mucoepidermoid breast carcinoma. A. Epidermoid and intermediate cells are positive for p63, whereas mucinous cells around the microcysts and toward the cystic lumen are mostly negative (The arrow points to a positive stain); (×100). B. Glandular cells are positive for CK 7 (The arrow points to a positive stain); (×200). C. Tumor cells are negative for calponin; (×100).