Breast mucoepidermoid carcinoma: A case report.

The present study reports the case of a 43-year-old female patient who underwent surgical excision of a right breast mass. Gross examination revealed a cystic lesion. Histopathological examination demonstrated a solid cystic tumor with intraluminal papillary projections. The neoplasm was composed of mildly atypical intermediate, epidermoid, mucinous and eosinophilic cells, exhibiting cribriform glandular patterns, and microcystic structures containing mucinous or eosinophilic secretions. Peritumoral lymphoid hyperplasia was observed in adjacent mammary gland tissue. Immunohistochemical results showed that p63, cytokeratin (CK) 5/6 and CK7 exhibited zonal positive staining; GATA binding protein 3 was positive; S-100 and SYN were negative; the estrogen receptor positive rate was 20%; progesterone receptor was negative; human epidermal growth factor receptor 2 was 1+; and the Ki-67 positive index was ~10%. Fluorescence in situ hybridization showed that the mastermind like transcriptional coactivator 2 gene was rearranged. The pathological diagnosis was low-grade mucoepidermoid carcinoma of the right breast. After diagnosis, the patient underwent a right breast-conserving surgery, right axillary sentinel lymph node biopsy and right breast fascial glandular flap plasty. Adjuvant radiotherapy was administered without endocrine therapy. Postoperative surveillance over 8 months showed no evidence of locoregional recurrence or distant metastasis.