Primary osteosarcoma (breast)

Last revised by Daniel J Bell on 12 Feb 2021

Primary osteosarcoma of the breast, a.k.a. extraskeletal osteosarcoma of breast, is an uncommon breast malignancy and is a subtype of extraskeletal osteosarcoma.

While it can present in a wide are group, the peak age at presentation is around the 6th decade 7.

The presence of bone in breast lesions is not diagnostic of osteosarcoma as osteoid tissue can be present in epithelial and mesenchymal neoplasms, both benign and malignant, such as fibroadenoma, phyllodes tumor 13, and metaplastic carcinomas. Therefore, a diagnosis of mammary osteosarcoma can only be established after a metaplastic carcinoma or biphasic tumor has been adequately excluded. Approximately 60% of tumors are grossly circumscribed 7.

Serum alkaline phosphate (ALP) levels are typically elevated.

Mammographic appearances can be variable. Most of the tumors presented as large masses with relatively well-defined margins and lobulated borders, often containing calcifications. Calcifications tend to be usually coarse (cotton wool like), dense, and sometimes similar to fibroadenomas.

Mammary osteosarcomas are aggressive tumors with a propensity for blood-borne rather than lymphatic spread. A total excision without an axillary dissection is usually part of standard treatment.

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