Malignant cylindroma may develop via malignant transformation of cylindroma in rare instances or may develop de novo in others. We present a case of malignant cylindroma located on the left parietal-occipital scalp that was treated twice by Mohs micrographic surgery in an attempt to excise the tumor completely and to minimize the excision of normal tissue. Our case is the sixteenth reported case of malignant cylindroma in the world literature.