100 transistors might be enough for a “triangulation” circuit. Hold three RF emitters around the tumor outside the patient’s body and the robot will navigate to

100 transistors might be enough for a “triangulation” circuit. Hold three RF emitters around the tumor outside the patient’s body and the robot will navigate to the point equidistant from all three emitters and start destroying tissue. You could move the orbs around to eat away the tumor, then filter them out of the bloodstream with a dialysis machine.