An unusual presentation of adenoid cystic carcinoma of the breast with metastatic disease in the clavicle

Adenoid cystic carcinoma (ACC) of the breast is a rare subtype of invasive breast cancer. Prognosis is excellent with low rates of recurrence and metastatic disease compared with other triple-negative forms of breast carcinoma and other non-breast forms of ACC. We present a case of a 63-year-old female with metastatic disease in the clavicle 13 years after excision of the breast primary. Metastasis to bone is rare, and this is the first case described in the clavicle. There are no specific radiological features of breast primaries but imaging usually reveals a circumscribed mass, often without microcalcifications. Histology is similar to that of non-breast forms of ACC. Mastectomy or wide local excision is curative in virtually all cases without lymph node involvement. However, as our case demonstrates, the presence of bone pain with a history of ACC of the breast should prompt musculoskeletal imaging. Discussion at a multidisciplinary team meeting is essential for accurate diagnosis.