RESUMEN
Adenoid cystic carcinoma (ACC) of the breast is a rare variant of breast malignancy and is associated with an excellent prognosis. ACC accounts for 0.1% of all breast carcinomas. It has favorable biological characteristics and an excellent prognosis. A 77-year-old woman presented with a lump in the right breast. Ultrasonography and mammography showed a 12-mm, well-defined, lobulated mass in the retroareolar region of the right breast. The lump was diagnosed as ACC on the basis of immunohistochemical staining results for c-kit (CD117), muscle-specific actin, p63, estrogen receptor, and progesterone receptor using a fine-needle aspiration cytology (FNAC) specimen. This diagnosis was subsequently confirmed by excision biopsy. To the best of our knowledge, this is the first case of ACC of the breast to date to be diagnosed on the basis of immunohistochemical staining of an FNAC cell block material. From our experience, we recommend the usage of cell block material for immunohistochemical studies to accurately diagnose ACC of the breast.