Ai ALI GNANCY OF TUMORS. Many tumors which are in themselves benign in character may be dangerous to life from their position and conse quent interference with the functions of impor tant organs. Such tumors, although sometimes causing death. are not classed as malignant tumors. Malignant tumors proper present cer tain well-defined characteristics of their malig nancy. Among these may be mentioned, first, their tendency to local recurrence after removal. This has led to the rule of the surgeon when operating on cancer to cut wide of the growth, even though the tumor may seem small and in significant. in the hope of removing all trace of cancerous tissue even at the sacrifice of some healthy tissue. This local recurrence after ap parently complete removal is undoubtedly due to the fact that cancer cells have extended out beyond the limits of the visible tumor. It is customary in some cases to have immediate mi croscopical examination made of the periphery of the mass removed, to determine the presence or absence of cancer cells at the outer limits of the operation. Secondly may he mentioned the tendency of a malignant tumor to extend by direct conti nuity of growth to surrounding tissues. In 'dis continuous peripheral growth' there are at first microscopic extensions outward of cancer cells from the periphery of the tumor. These grow
;Ind form nodules near, though at first separated from, the main tumor mass, but which after wards spread and usually join the original tumor. A third and very eharacteristic mark of malignancy in a tumor is the formation of what are known as metastatic tumors. These are sec ondary tumors of the same general nature as the parent growth. They may occur in any tis sue or organ, no matter bow distant, and are the result of cancer cells disseminated through the blood and lymph. These cells, lodging, form the starting points of new or secondary or meta static growths. These secondary growths may also act as new centres of infection from which other metastatie tumors may arise. A fourth evidence of malignancy is the effect of the Pres enee of tile cancer upon the general health of the patient. General impairment of the patient's health is due to many factors, such as time drain upon the whole system of a rapid new growth, the absorption of injurious matter from the tumor itself, the effect of suppuration o• necro sis, etc., and is known as 'cancerous cachexia.'