Derm Dx: Simultaneous appearance of multiple indurated plaques

A 70-year-old man presents with skin lesions located on his back, left thigh, and scalp. These arose simultaneously approximately 4 weeks previously. He is in good health and is a nonsmoker. He takes omeprazole for gastric reflux. He denies fatigue, weight loss, or swollen glands. Examination reveals several dusky red indurated plaques.