A 79-year-old woman was treated in our ward for an invasive carcinoma of no special type (NST) of her left breast, discovered by a spontaneous apparition of a localized ecchymotic lesion of the breast. The unique calling-spot was this 4x5cm homogeneous oval shape purpura without any notion of trauma, stable for months. The patient have no medical history of thrombopenia nor allergies. The physical exam was poor, without any palpable breast lesion. A not well defined solid para-areolar structure of 11 mm was found during the senological assessment. Biopsies were performed and highlighted a grade II NST, triple negative, Ki67 15%. The axillary cytology was positive. Subsequently this atypical presentation, a punch biopsy was performed on the ecchymosis. The histology showed the presence of dermal lymphatic carcinomatous emboli that may correspond to a mammary origin, and blood extravasations in the dermis, explaining the ecchymotic aspect. The PET-CT was negative. Neo-adjuvant chemotherapy was decided before mastectomy and axillary dissection. This was a rare clinical presentation of a locally advanced breast cancer without any reported similar case. Usually, the presence of emboli with carcinoma cells obstructing lymph ducts is associated with an inflammatory breast cancer. The presence of tumor emboli in the lymph ducts comes out in favor of the diagnosis but it is not mandatory. Moreover, dermal lymphatic invasion without typical clinical presentation isn’t sufficient to diagnose a carcinomatous mastitis. A main criterion is the rapidity of the worsening of the symptoms which is not obvious in that case with a stagnation of the skin lesion for months. The skin lesion of our patient could be suspected of being a mammary angiosarcoma. This possibility was quickly put aside with the absence of vascular tumoral proliferation on the biopsies. Every acute purpura is a serious condition to diagnose in emergency to not miss a meningococcemia, a severe thrombopenia or an infective endocarditis. Any isolated purpura of the breast must set off a senological assessment and cutaneous biopsies, when the clinical presentation is atypical and in absence of patent diagnosis, in order not to miss an underlying, locally advanced neoplasia.