The very original definition of carcinomatous mastitis suggests the main diagnostic difficulty of this onchologic condition. Actually it is more correctly appointed as inflammatory breast cancer, because notwithstanding the inflammatory appearance, it is a true systemic breast cancer, for which surgery represents an only marginal treatment resource. If is now well known that radical mastectomy is ineffective and only a combination of CT and RT offers survival results of some value. But the actual correct multi modal treatment cannot be undertaken if not after a correct diagnostic confirmation, avoiding an anti-inflammatory therapeutic attempt that is time consuming and possibly deceptive. Surgery and histology can be the only means of a correct diagnosis when FNAB is falsely negative, but the lymph nodes must be the preferential tissue to examinate to avoid long lasting drainage from the breast parenchyma after a biopsy, that delays the beginning of the true treatment.