Syringoma-like eccrine sweat duct proliferation induced by radiation.

We report a 45-year-old woman with breast cancer who had undergone surgery and radiation and anti-estrogen therapy and presented with many reddish papules in the irradiated breast area. Skin biopsy of the affected area disclosed proliferation of eccrine sweat ducts and cystic structures; the clinical and histopathological features were consistent with syringoma-like eccrine sweat duct proliferation. The lesions spread rapidly on her chest during radiation therapy and regressed spontaneously 3 weeks after its completion. We postulate that the lesions were induced by radiation, and promoted by anti-estrogen therapy.