A woman in her 60s presented for evaluation of a new pruritic rash. The rash initially developed on the patient鈥檚 legs 13 days before presentation and subsequently progressed to her feet, arms, hands, and trunk. Associated symptoms included a burning sensation and occasional pain. Her medical history was notable for endometrial adenocarcinoma status post hysterectomy and recent postoperative radiotherapy (total of 50.4 Gy in 28 fractioned doses), which was completed 4 days after the onset of the rash. She denied any new medications or exposure to chemotherapy, imaging with intravenous contrast, or recent travel. The remainder of her review of systems was unremarkable. On physical examination, there were numerous erythematous edematous coalescing papules and plaques on the upper and lower extremities and scattered erythematous papules and plaques on the back and buttocks (Figure, A). Some plaques were annular and polycyclic in configuration, with central hyperpigmentation (Figure, B). Her chest, abdomen, face, and oral mucosa were clear. A complete blood cell count was notable for an eosinophilia of 11%, with an absolute cell count of 0.80 脳103/uL. Results from a comprehensive metabolic panel were normal. A biopsy was performed on her right thigh for histopathological examination.