Change of Pathological Type to Metaplastic Squamous Cell Carcinoma of the Breast During Disease Recurrence: Case Report and Literature Review.

Metaplastic squamous cell carcinoma (SCC) of the breast is a rare and heterogeneous group of primary breast malignancies. The etiology, pathogenesis, and proper treatment for this kind rare breast cancer are still unclear. We reported a case of a 55-year-old woman with a palpable lump in the inner quadrant of the right breast. She underwent a right breast mass resection and sentinel lymph node biopsy, which revealed that the tumor was an invasive ductal carcinoma, followed by four cycles of doxorubicin plus cyclophosphamide and four cycles of docetaxel as adjuvant chemotherapy, and then simultaneous integrated boost intensity modulated radiotherapy to the whole right breast. After 2 years' follow-up, she had biopsy-proven disease recurrence in the right breast, which revealed SCC, and a mammogram showed abnormalities in the lower inner quadrant of the right breast and left axillary lymph nodes. Then we performed bilateral breast modified radical mastectomy, which confirmed that the recurrent tumors were metaplastic SCC, followed by adjuvant chemotherapy and adjuvant radiotherapy of the left supraclavicular and apical axillary regions. There has been no recurrent or metastatic evidence in the 16 months' follow-up since the second surgery. This case report shows that evolution of pathology type in recurrent breast cancer after initial treatment is possible. Detailed pathologic and immunohistochemical analyses are needed for identification of this change. Surgery and adjuvant radiation and chemotherapy are appropriate treatments for recurrent primary SCC of the breast.