Surgical cure requires that a given cancer be removed without inadvertent spillage of cancer cells by technical error. Potential mishaps include pressing a ligature, while tying, against a protruding tumor and cutting into it; inserting a hemostat into the tumor area to gain control of an escaped short pancreaticoduodenal artery stump which has retracted; grasping a lymph node with forceps which invariably fragments it spilling any cancer cells it may contain; and injecting local anesthesia into or adjacent to a lesion for biopsy. If the lesion is a cutaneous melanoma or other cancer the resulting pressure may force cancer cells into the lymphatic or bloodstream. Other misadventures include touching that portion of a biopsy needle which has been in the tumor and doing an intraoperative biopsy which allows blood or tissue fluid to flow out the opening from the tumor. Sensitivity to such dangers appears essential to avoiding spillage of cancer cells and obtaining maximal benefit from surgery.