A woman in her 70s presented with a 1-month history of multiple tense bullae on the right breast associated with worsening erythema and tenderness. Four months prior, she had completed radiation therapy (RT) to this site (total energy dose, 50 Gy [to convert to rad, multiply by 100]) for treatment of invasive ductal breast carcinoma. She was initially treated with dicloxacillin sodium for possible bullous impetigo after a culture demonstrated Staphylococcus aureus but was then hospitalized for administration of broad-spectrum intravenous antibiotics after demonstrating no clinical improvement. On physical examination, there were multiple tense 0.5- to 3-cm bullae localized to the right breast (Figure, A and B). The bullae, as well as multiple erosions and surrounding erythema, occurred within the previously irradiated site, as demarcated by radiation tattoos (Figure, A). There was no involvement of mucosal membranes. Punch biopsies were performed (Figure, C and D).