Pyoderma gangrenosum of the breast: a diagnosis not to be missed.

Pyoderma gangrenosum (PG) is a non-infectious purulent ulcerative disease triggered mainly by chronic inflammatory bowel disease, monoclonal gammapathy, polyarthritis and haematological malignancies; exceptionally, it can be triggered by surgery alone. When PG is associated with fever, it can mimic infectious cellulitis. When it is located on the breast, unnecessary and deleterious surgical debridement may be performed. We present two cases of PG of the breast. The first is a postoperative PG and the second was associated with acute myeloid leukaemia - both led to unnecessary surgery. Several elements may have helped to make the diagnosis: nipples little affected by PG, symmetrical lesions on both breasts, other similar lesions elsewhere on the body, resistance to wide spectrum antibiotherapy, complete blood count abnormalities and negativity of bacterial culture. We propose an index to help the surgeon in his decision to realise a surgical debridement or to postpone it and consider the diagnosis of PG.