From the Guidelines
Tumor seeding after an injection is a rare but serious complication where cancer cells are inadvertently spread along the path of a needle, with a reported risk of 2.7% after liver biopsy, according to a meta-analysis 1. This complication occurs when the needle passes through cancerous tissue and then through healthy tissue, potentially depositing malignant cells along the needle track. The risk of tumor seeding varies by cancer type, with higher risks in certain aggressive cancers. To minimize this risk, healthcare providers use specific techniques such as coaxial needle systems and choosing the shortest possible needle path. For patients undergoing biopsies of suspicious masses, the benefit of obtaining diagnostic information typically outweighs the small risk of tumor seeding. Key factors to consider include:
- The type of cancer being biopsied
- The technique used for the biopsy or injection
- The experience of the healthcare provider performing the procedure
- The potential consequences of not performing the biopsy or injection. As reported in the study 1, needle track seeding can be treated well, e.g., by excision or radiation, and does not affect the outcome of oncological treatment or overall survival. Therefore, the potential risks of tumor seeding should not be seen as a reason to abstain from diagnostic procedures, as the benefits of obtaining diagnostic information typically outweigh the small risk of this complication 1.
From the Research
Definition of Tumor Seeding
Tumor seeding refers to the process by which tumor cells are dislodged from the primary tumor site and implanted into other areas of the body, often along the needle track, during diagnostic or therapeutic procedures such as fine-needle aspiration cytology (FNAC) or core needle biopsy 2, 3, 4, 5, 6.
Risk of Tumor Seeding
The risk of tumor seeding is considered to be low, with estimated incidence rates ranging from 0.00012% to 0.0011% after FNAC and core needle biopsy, respectively 4. However, the actual risk may be higher due to underreporting of cases.
Factors Contributing to Tumor Seeding
Several factors have been implicated in the risk of tumor seeding, including:
- Needle size and type 4
- Number of needle passes 4
- Type of tumor (benign or malignant) 4
- Location of the tumor (e.g. salivary glands, cervical lymph nodes) 4
Clinical Implications
Tumor seeding can have significant clinical implications, including the potential for implantation metastases and compromised outcomes of radical surgery 6. Therefore, diagnostic procedures such as FNAC and core needle biopsy should only be performed when the result has a direct impact on the choice of therapy.
Reported Cases
Several cases of tumor seeding have been reported in the literature, including cases after FNAC of benign parotid tumors 2, percutaneous ethanol injection therapy for hepatocellular carcinoma 3, and fine-needle biopsy of abdominal malignancies 6. These cases highlight the importance of considering the risk of tumor seeding when performing diagnostic or therapeutic procedures.