The first part of this article deals with the report of a patient suffering from pyoderma gangrenosum of the "sinus mammarum" associated with asymptomatic ulcerative colitis. This is followed by a revision of the present epidemiological, etiological, pathogenetic and clinical knowledges about this systemic manifestation of chronic phlogosis of the colon. The Authors have analysed the treatment for this condition and emphasized the resistance of the cutaneous ulcer encountered to conventional medical therapy of the underlying colonic disease which proved to be efficacious only on the latter; this led to integrate traditional treatment with the use of perilesional injections of small doses of calcic heparin as an alternative to immunosuppressive drugs or surgery. Topical antithrombotic treatment, which can be justified by the histological findings of phenomena of the vasculitis in the edge of pyoderma gangrenosum, demonstrated to be crucial and represents a peculiarity in the case here reported, which is unique in the literature as far as the Authors know, since it has not been experimented by anyone else.