A 78 year-old female patient underwent a
total mastectomy with axillary lymph node dissection for
a primary breast osteosarcoma. Microscopically the
tumor was identical to grade II skeletal osteosarcoma.
Immunohistochemically no reactivity was detected,
either for the epithelial markers EMA, AE1/AE3, CK8,
18, 19, or for HER-2/neu, estrogen and progesterone
receptors, as well as fluorescent IN SITU hybridization
for HER-2/neu. The diagnosis of this tumor fulfills
certain clinicopathological criteria. Mammary
osteosarcoma is usually developed in phyllodes tumors
or carcinosarcomas of the breast as a result of metaplasia
of the epithelial component. This rare tumor of the breast
is occasionally associated with prior radiation therapy or
well documented trauma. Mammary osteosarcoma is a
biologically aggressive neoplasm with a 38% five-year
survival rate. Surgical resection is the most effective
therapy to date. Adjuvant treatment -chemotherapy or
radiotherapy- has shown no clear benefit. An extensive
review of the literature is also presented.