We present a case of pyoderma gangrenosum localized on the breast, without a preceding surgical intervention and associated systemic disorder. The ulcer had rapidly developed and covered a large portion of the breast. The patient responded well to systemic steroids and salicylazosulfapyridine and the ulcer completely healed with scarring after 3 months of treatment. Pyoderma gangrenosum rarely involves the breasts. A published work survey disclosed only 31 reported cases up to date. In most of these cases the lesions were related to previous surgical interventions, probably as the result of a pathergy phenomenon. The main differential diagnoses were skin and soft tissue infections including necrotizing fasciitis, and malignant neoplasms. Negative initial wound cultures and the relative sparing of nipple/areola complex helped to eliminate these disorders. Though an unusual site for pyoderma gangrenosum, lesions on the breast showed the characteristic clinical features of the disease. The types of associated disorders were also similar to those of the cases with classical pyoderma gangrenosum. As most of the lesions healed with significant scarring, early recognition and treatment of pyoderma gangrenosum located on the breast is important to prevent serious physical and psychological morbidity.