Can a cancer biopsy cause metastases?

Cancer Biopsy Does Not Typically Cause Metastases

Cancer biopsies are generally safe procedures that do not cause metastases in most clinical scenarios. While there are theoretical concerns about tumor cell dissemination during biopsy procedures, current evidence and clinical guidelines support the safety and necessity of biopsies in cancer diagnosis and management.

Evidence from Guidelines on Biopsy Safety

Biopsy Recommendations in Clinical Practice

Multiple clinical guidelines recommend biopsies as essential diagnostic procedures across various cancer types:

• The NCCN guidelines for melanoma recommend sentinel lymph node biopsy (SLNB) as a standard procedure for appropriate patients with no evidence that this procedure causes metastatic spread 1.

• The British Journal of Cancer guidelines for soft tissue sarcomas state that "the risk of seeding a metastasis in a biopsy tract is very small" and emphasize that obtaining a pre-treatment histological diagnosis by core biopsy should not be undermined by concerns about tumor spread 1.

• The AASLD guidelines for hepatocellular carcinoma acknowledge the theoretical risk but still recommend biopsy when needed for diagnosis, noting that concerns about complications should be balanced against the need for accurate diagnosis 1.

Biopsy's Role in Treatment Planning

Biopsies are increasingly recognized as crucial for optimal cancer management:

• The ASCO guidelines for breast cancer recommend biopsy of metastatic sites when feasible to confirm diagnosis and assess biomarker status, as discordance between primary and metastatic sites can occur and affect treatment decisions 1.

• The NCCN guidelines for CNS cancers state that "if no other readily accessible tumor is available for biopsy, a stereotactic or open biopsy resection is indicated to establish a diagnosis" 1.

Rare Cases of Tumor Seeding

While extremely uncommon, there have been isolated case reports of potential tumor seeding:

• A case report described possible needle track dissemination of papillary thyroid carcinoma after fine needle aspiration biopsy, with metastatic deposits appearing in the skin and muscle four years after the procedure 2. However, this represents an exceptionally rare occurrence rather than a common risk.

Evolving Alternatives: Liquid Biopsy

Recent research has focused on developing less invasive alternatives to traditional tissue biopsies:

• Liquid biopsy techniques analyze circulating tumor cells or tumor-derived cell-free nucleic acids in blood samples, potentially offering a less invasive alternative that might reflect all tumor subclones present at a specific time point 3, 4, 5.

• These techniques may be particularly valuable in cases where traditional biopsies are difficult to perform or when monitoring disease evolution over time.

Best Practices to Minimize Risks

When performing biopsies, certain precautions can further reduce any theoretical risk:

• The British guidelines for radiologically guided lung biopsy recommend planning the biopsy tract so it can be safely removed during definitive surgery if needed 1.

• Core needle biopsies under image guidance are preferred for many tumor types to minimize trauma while obtaining adequate tissue 1.

Conclusion

The benefits of obtaining accurate diagnostic information through biopsy far outweigh the extremely small theoretical risk of tumor seeding. Biopsies remain essential for:

1. Establishing a definitive diagnosis
2. Determining cancer subtype and biomarker status
3. Guiding appropriate treatment selection
4. Monitoring disease evolution and treatment response

While extremely rare cases of tumor seeding have been reported, they should not deter clinicians from performing necessary biopsies when indicated for optimal patient care.