Adenoid Cystic Carcinoma, Solid-Basaloid Subtype of the Breast: A Case Report

We present a rare tumor of adenoid cystic carcinoma, solid-basaloid subtype of the breast. Solid-basaloid adenoid cystic carcinoma may have a worse prognosis than classical adenoid cystic carcinoma. A 70-year-old woman presented with a mass in her left breast. Malignancy was suspected on imaging and confirmed via core needle biopsy. Left breast partial mastectomy and sentinel lymph node biopsy were performed. Histologically, the tumor was composed of basaloid cells with hyperchromatic nuclei and frequent mitotic figures, as are small-cell neuroendocrine carcinomas. Immunohistochemical analysis of the tumor cells showed high expression of KIT and CD10 and focal expression of keratin 7. Synaptophysin, chromogranin A, estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 were not expressed. This patient should be followed up carefully for distant metastases and recurrences.