In addition to its tendency to infiltrate adjacent tissues and organs, cancer is also liable to give rise to secondary growths.  These are most often met with in the nearest lymph glands; those in the neck, for example, becoming infected from cancer of the lip, tongue, or throat; those in the axilla, from cancer of the breast; those along the curvatures of the stomach, from cancer of the pylorus; and those in the groin, from cancer of the external genitals.  In lymph vessels the cancer cells may merely accumulate so as to fill the lumen and form indurated cords, or they may proliferate and give rise to secondary nodules along the course of the vessels.  When the lymphatic network in the skin is diffusely infected, the appearance is either that of a multitude of secondary nodules or of a diffuse thickening, so that the skin comes to resemble coarse leather.  On the wall of the chest this condition is known as cancer en cuirasse.  Although the cancer cells constantly attack the walls of the adjacent veins and spread into their interior at a comparatively early period, secondary growths due to dissemination by the blood-stream rarely show themselves clinically until late in the course of the disease.  It is probable that many of the cancer cells which are carried away in the blood or lymph stream undergo necrosis and fail to give rise to secondary growths.  Secondary growths present a faithful reproduction of the structure of the primary tumour.  Apart from the lymph glands, the chief seats of secondary growths are the liver, lungs, serous membranes, and bone marrow.

It is generally believed that the secondary growths in cancer that develop at a distance from the primary tumour, those, for example, in the medullary canal of the femur or in the diploe of the skull occurring in advanced cases of cancer of the breast, are the result of dissemination of cancer cells by way of the blood-stream and are to be regarded as emboli.  Sampson Handley disagrees with this view; he believes that the dissemination is accomplished in a more subtle way, namely, by the actual growth of cancer cells along the finer vessels of the lymph plexuses that ramify in the deep fascia, a method of spread which he calls permeation.  It is maintained also that permeation occurs as readily against the lymph stream as with it.  He compares the spread of cancer to that of an invisible annular ringworm.  The growing edge extends in a wider and wider circle, within which a healing process may occur, so that the area of permeation is a ring, rather than a disc.  Healing occurs by a process of “peri-lymphatic fibrosis,” but as the natural process of healing may fail at isolated points, nodules of cancer appear, which, although apparently separate from the primary growth, have developed in continuity with it, peri-lymphatic fibrosis having destroyed the cancer chain connecting the nodule with the primary growth.  This centrifugal spread of cancer is clearly seen in the distribution of the subcutaneous secondary nodules so frequently met with in the late stages of mammary cancer.  The area within which the secondary nodules occur is a circle of continually increasing diameter with the primary growth in the centre.