Figure 4: A primary tumor (black irregular shape) is associated with a complex field of molecular alterations in structurally intact cells in histologically normal adjacent tissue (arrows and dotted lines; left). After focal therapy to the primary tumor (white dashed lined irregular shape), premalignant areas (grey irregular shapes) may in time lead to onsite or secondary tumors within the remaining field (upper right). If focal therapy is extended to include the field, onsite recurrences could be avoided (lower right).