Giant cell arteritis is an inflammatory lesion of the large- and medium-sized arteries, usually involving the temporal arteries of older women. Rarely, the breast has been reported as the primary site of involvement. Patients usually present with breast masses that are tender or painful in most reported cases. The disease may be associated with constitutional symptoms that resemble polymyalgia rheumatica, but most reported cases do not have an established diagnosis of autoimmune disease. Clinically, giant cell arteritis of the breast may mimic breast carcinoma. Establishing the diagnosis is important because most patients achieve remission of symptoms after treatment with prednisone.