Seeding after US-guided biopsy

Percutaneous needle biopsy is almost exclusively performed under imaging guidance, using either ultrasound or computed tomography. Although accepted as a relatively safe procedure, percutaneous needle biopsy is certainly not risk-free. One of the potential serious complications after a percutaneous biopsy is tumor seeding which is relatively poorly understood and documented. Neoplasm seeding is defined as a local implantation of tumor cells by contamination of instruments and surgical equipment resulting in local growth of the cells and tumor formation (according to the National Library of Medicine of the National Institutes of Health, USA). Frequency and mechanisms behind tumor seeding after biopsy are poorly elucidated. In the four largest surveys the range of the needle tract seeding after biopsy of abdominal lesions was miniscule (0–0.009%). Common to these relatively old studies was that they were based on patient and doctor reporting, without performing an active cross-sectional imaging verified tracing of seeding; and therefore the true seeding rate was probably greatly underestimated. Sparsely documented incidences in the more recent studies of the colorectal neoplasm seeding following liver biopsy vary between 10% and 19%. These data consist primarily of relative small case series and reports limited by small sample size. The reported high seeding rates are therefore probably greatly overestimated in these studies. Some authors suggest that invasive diagnostic procedures should be carefully considered due to risk of seeding which can change a potentially respectable localized cancer to an unrespectable one. Neoplasm seeding has been a subject of particular concern for liver surgeons. Tumor seeding is a well-known phenomenon after traditional open surgical procedures as well as after laparoscopic procedures. Tumor seeding has also been reported after ultrasound guided radiofrequency ablative procedures. Experimental studies have shown cancer cell leakage in the needle tract in the majority of biopsy cases. How do we reduce tumor seeding? The co-axial biopsy technique, whereby the biopsy needle is inserted through an introducing needle, is popular with many practitioners who cite improved needle stability and the ability to obtain multiple cores using only one initial puncture as strong advantages of this system. It has been suggested that the co-axial technique reduces the risk of needle tract seeding by isolating the biopsy specimen from the needle tract when the sample is withdrawn. Unfortunately no randomized studies have proved this yet. Furthermore, seeding after using the co-axial biopsy technique has been described. The use of contrast enhanced ultrasound can reduce the need for ultrasound guided liver biopsy in many cases, and this procedure should be reserved to unclear cases approved by the local multidisciplinary team and to cases where oncologic treatment is planned.