Patients with breast cancer normally present with breastlump or abnormal mammogram. Dermatomyositis is rarelythe first presentation. We present a case of a 63-year-oldwoman who had generalised dermatitis, progressive fatigueand muscle weakness. She was first diagnosed asdermatomyositis and subsequently breast cancer. Her rashand muscle weakness progressed drastically over a month.Tumescent mastectomy and axillary surgery was performed,which led to gradual regression of her dermatomyositis oversix months. This case report emphasized in the benefit ofearly diagnosis and treatment of dermatomyositis andbreast cancer. Pros and cons of tumescent mastectomy isdiscussed as well.