Where does breast cancer tend to metastasize to?

Breast Cancer Metastatic Sites

Bone is the most common site of breast cancer metastasis, occurring in 51% of cases, followed by liver/soft tissue (19%), pleura (16%), lung (14%), and brain (4%). 1

Primary Metastatic Sites by Frequency

The hierarchy of metastatic spread follows a predictable pattern:

• Bone metastases dominate as the first site of distant spread, affecting up to 70% of women with stage IV disease 1, 2
• Liver involvement occurs in approximately 50% of patients with stage IV disease during their disease course, though it is less common as the initial metastatic site 2
• Lung metastases represent 14-17% of initial distant spread 1, 3
• Brain metastases occur in 4-16% of cases, with breast cancer being the second most common cause of intracerebral metastases after lung cancer 1, 2

Metastatic Patterns by Molecular Subtype

The molecular subtype of breast cancer critically determines the pattern of organ-specific spread:

Luminal (ER/PR Positive) Cancers

• Predominantly metastasize to bone, with 82% of patients who develop bone metastases having ER and/or PR positivity in the primary tumor 1, 2
• Carry a long-term risk of recurrence, especially to bone, even years after initial diagnosis 1
• Up to 13.6% of women with early-stage disease will develop bone metastasis within 15 years, even with low-grade primary tumors 1

HER2-Enriched Cancers

• Preferentially spread to liver and lung 1, 2
• Demonstrate a higher rate of recurrence in the first 4 years compared to luminal subtypes 1, 2

Triple-Negative/Basal-Like Cancers

• Commonly metastasize to liver and brain 1, 2
• Show no predilection for bone metastases, unlike other subtypes 2
• Have a higher rate of recurrence in the first 4 years 1
• Display lung tropism in basal-like breast cancer 4

Prognostic Implications by Metastatic Site

The location of metastasis significantly impacts survival outcomes:

• Liver metastases carry the worst prognosis, with median survival of only 1 month without intervention and 3-15 months with multimodal treatment including surgical resection in selected patients 2
• Brain metastases have a median survival of 3 months and are the leading cause of death in breast cancer due to limited blood-brain barrier permeability and lack of effective treatments 2, 5
• Bone and lung metastases have a median survival of 12 months 3
• Multiple metastatic sites (including brain) significantly reduce survival to 3-15 months depending on cancer subtype and performance status 2

Critical Clinical Pitfalls

• Peripheral bone metastases are almost always (>99%) accompanied by extraosseous or central osseous metastasis, and their detection rarely changes management 2
• False-positive rates on chest CT requiring additional imaging range from 10-33% in asymptomatic women 2
• Time until relapse does not correlate with survival after metastasis—patients who develop distant metastases soon after initial diagnosis have the same postmetastatic prognosis as those whose disease metastasizes later 3