The margin, while in parts irregular, is typically represented by a well-defined “rolled” border which consists of the peripheral portion of the cancer that has not broken down.  The central ulcer may temporarily heal.  There is itching but little pain, and the condition progresses extremely slowly; rodent cancers which have existed for many years are frequently met with.  The disease attacks and destroys every structure with which it comes in contact, such as the eyelids, the walls of the nasal cavities, and the bones of the face; hence it may produce the most hideous deformities (Fig. 103).  The patient may succumb to haemorrhage or to infective complications such as erysipelas or meningitis.

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 Rontgen 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