RESUMEN
BACKGROUND: Breast cancer occupies the chief place in incidence after the cervix. This gland sarcomas are rare with less than 1% at this location. Its diagnosis is difficult and its evolution is aggressive. Primary breast osteogenic sarcomas are a subset of lower frequency so that their behavior, evolution, prognosis ytratamiento no much experience and often are diagnosed as benign tumors. CASE REPORT: We report the case of a woman of 59 years which initially arose from a tumor in the right breast was performed with tru-cut biopsy with inconclusive results, using the tumor 7 months after the presence of a multilobulated solid tumor 20 cm, tumor compatible with mammography Phylodes (BIRADS 2). It was decided to perform right total mastectomy and pectoral muscle resection reconstruction with latissimus dorsi more and histochemical review pathology diagnosed with malignant mesenchymal neoplasm, osteosarcoma osteoblast osteoclast type and complemented the treatment with radiotherapy and chemotherapy. The prognosis is poor because the five-year survival is less than 40%. CONCLUSION: In the fast-growing breast tumors and large mammographic calcifications with signs and antecedentesde irradiation, trauma and Phyllodes tumor must be aware of this disease and that early diagnosis improves survival. In the surgical treatment of axillary dissection is not indicated and adjuvant treatment with radiotherapy and chemotherapy.