Development of distant keratoacanthomas (KAs) while undergoing vismodegib therapy. A, Clinical photograph of the rapid-onset 2-cm nodule on the right arm of patient 1 after 2 weeks of vismodegib treatment for an eyelid basal cell carcinoma (BCC). B, Histologic image from case 1 shows a cup-shaped, well-differentiated squamous cell carcinoma (SCC) invaginating into the dermis that was filled with keratin, consistent with KA (hematoxylin-eosin, original magnification ×100). C, Clinical photograph of KA development on the inferior medial brow of patient 2 after 7 weeks of vismodegib therapy for a periocular BCC. D, Histologic image shows a well-differentiated SCC, or KA (hematoxylin-eosin, original magnification ×100).