Metastases to the breast

Last revised by Ammar Ashraf on 12 May 2021

Metastases to the breast from non-mammary primary tumors are uncommon and account for 0.5-2.0% of all breast malignancies. 

Metastases do not tend to cause retraction of the skin or nipple. Metastatic lesions are much more likely to be multiple or bilateral than primary cancers. 

Breast metastases from extra-mammary malignancies are unusual, and if present, typically indicate widely disseminated disease. They tend to be found in the subcutaneous fat, whereas primary breast cancers develop in glandular tissue.

The most frequent source of a metastatic breast lesion is the contralateral breast 2. The most common extra-mammary cancers that metastasize to the breast are:

Like other metastasis, metastases to the breast tend to be rounded and well defined. As opposed to breast cancer, calcification is unusual.

On mammography, metastatic lesions may manifest as single or multiple masses or as diffuse skin thickening. Metastases usually appear as round masses with circumscribed or ill-defined borders. They typically lack spiculation. Microcalcifications are rare can occur with some primary type (e.g, psammoma bodies in ovarian cancer).

On ultrasound, metastatic masses tend to have circumscribed margins with low-level internal echoes and, occasionally, posterior acoustic enhancement. Color Doppler interrogation most often shows increased vascularity.

The first case of a metastatic lesion to the breast is thought to have been reported by Trevithick in 1903 4.

On mammography several other primary breast lesions may easily mimic that of a typical well-defined metastasis which may be benign or malignant:

Rarely, metastasis to the breast may be spiculated and mimic an invasive ductal carcinoma.

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Cases and figures

  • Case 1: neuroendocrine tumor
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  • Case 2: "miliary" from contralateral breast cancer
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  • Case 3: renal cell carcinoma
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  • Case 4: liposarcoma
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  • Case 5: malignant melanoma
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  • Case 6: small-cell lung cancer
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  • Case 7: renal cell cancer
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  • Case 8: embryonal rhabdomyosarcoma
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