Radiation recall dermatitis is one of the skin sequelae that may affect oncology patients. It occurs in a previously irradiated field, when subsequent chemotherapy is given. The eruption may be elicited by chemotherapy, even several months after radiotherapy. Its mechanism is poorly understood, and the histopathologic findings have received, to date, only sketchy descriptions. A 55-year-old male affected by multiple myeloma received radiation therapy both on his left coxofemoral area, and lumbar region (D11-L1). After cyclophosphamide administration, he developed 2 well defined square-shaped, infiltrated erythematoviolaceous plaques in the prior irradiated fields. Histopathologic findings revealed a diffusely fibrosclerosing process, involv...