Abstract: A method for locating a lesion within a tissue mass, includes steps of measuring a selected parameter at two or more points in at least one path through the tissue mass, the measure of the selected parameter in a lesion being different from that in normal tissue. Also, apparatus for measuring a tissue parameter at two or more points in at least one path through the tissue mass includes an insertion needle, distally sharpened and made sufficiently rigid so that it can be inserted distal end foremost into the tissue mass along the path, and, insertible with the needle, a sensor capable of prodding a measure of the tissue parameter at a point in the tissue mass along the path. Where the parameter is selected as one that has a measure different in a lesion type, the apparatus can be used in carrying out the method, whereby a measure at a point in the tissue mass of the selected tissue parameter provided by the sensor indicates that the point is within a lesion.