Secondary growths in the lymph glands, while not unknown, are extremely rare. We have only seen them once—in a case of rodent cancer in the groin.
Diagnosis.—Lupus is the disease most often mistaken for rodent cancer. Lupus usually begins earlier in life, it presents apple-jelly nodules, and lacks the rounded, elevated border. Syphilitic lesions progress more rapidly, and also lack the characteristic margin. The differentiation from squamous epithelioma is of considerable importance, as the latter affection spreads more rapidly, involves the lymph glands early, and is much more dangerous to life.
Treatment.—In rodent cancers of limited size—say less than one inch in diameter—free excision is the most rapid and certain method of treatment. The alternative is the application of radium or of the Röntgen rays, which, although requiring many exposures, results in cure with the minimum of disfigurement. If the cancer already covers an extensive area, or has invaded the cavity of the orbit or nose, radium or X-rays yield the best results. The effect is soon shown by the ingrowth of healthy epithelium from the surrounding skin, and at the same time the discharge is lessened. Good results are also reported from the application of carbon dioxide snow, especially when this follows upon a course of X-ray treatment.
Paget's disease of the nipple is an epithelioma occurring in women over forty years of age: a similar form of epithelioma is sometimes met with at the umbilicus or on the genitals.
Melanotic Cancer.—Under this head are included all new growths which contain an excess of melanin pigment. Many of these were formerly described as melanotic sarcoma. They nearly always originate in a pigmented mole which has been subjected to irritation. The primary growth may remain so small that its presence is not even suspected, or it may increase in size, ulcerate, and fungate. The amount of pigment varies: when small in amount the growth is brown, when abundant it is a deep black. The most remarkable feature is the rapidity with which the disease becomes disseminated along the lymphatics, the first evidence of which is an enlargement of the lymph glands. As the primary growth is often situated on the sole of the foot or in the matrix of the nail of the great toe, the femoral and inguinal glands become enlarged in succession, forming tumours much larger than the primary growth. Sometimes the dissemination involves the lymph vessels of the limb, forming a series of indurated pigmented cords and nodules ([Fig. 104]). Lastly, the dissemination may be universal throughout the body, and this usually occurs at a comparatively early stage. The secondary growths are deeply pigmented, being usually of a coal-black colour, and melanin pigment may be present in the urine. When recurrence takes place in or near the scar left by the operation, the cancer nodules are not necessarily pigmented.
Fig. 104.—Diffuse Melanotic Cancer of Lymphatics of Skin secondary to a Growth in the Sole of the Foot.
To extirpate the disease it is necessary to excise the tumour, with a zone of healthy skin around it and a somewhat large zone of the underlying subcutaneous tissue and deep fascia. Hogarth Pringle recommends that a broad strip of subcutaneous fascia up to and including the nearest anatomical group of glands should be removed with the tumour in one continuous piece.
Secondary Cancer of the Skin.—Cancer may spread to the skin from a subjacent growth by direct continuity or by way of the lymphatics. Both of these processes are so well illustrated in cases of mammary cancer that they will be described in relation to that disease.