Seeding—the transfer of tumor cells from a dislodged biopsy needle—is not impossible but very rare, according to the American Society of Clinical Oncology (ASCO). One review of studies in BJU International found the incidence to be less than 1%. Another study, in Gut, found no increased risk of dying among people with pancreatic cancer who had biopsies. A 2019 study in Urology found no evidence of seeding at all among 42 patients with bladder cancer followed for 28 months.

“Properly performed, biopsies often provide essential information to help diagnose, stage and inform clinical decision-making for patients with suspected or known cancer,” says ASCO editorial board member Jeffrey E. Gershenwald, MD, a professor of surgical oncology at MD Anderson Cancer Center in Houston.