As a result of long-continued exposure to the x-ray, chronic dermatitis very commonly develops. The superficial cells become necrotic, but in addition there is an involvement of deeper structures. Necrotic foci occur in the corum, probably due to vesicular disturbances, such as narrowing of the lumen of the vessels due to a proliferation of the endothelium. These deeper lesions may remain quiescent, but eventually the epidermis undergoes a downward proliferation, invades these foci, takes on an infiltrating character, and may give rise to very extensive metastases. The fingers and hands are usually the site of the primary lesion or lesions. The histologic structure of these growths is that of the squamous epithelioma.

Rodent ulcer or carcinoma basocellulare arises from the basal cells of the epidermis, particularly from those cells in the hair-follicles. Are most common in the region of the eyes and nose, usually occurring in men.

For many years - 'from three to twelve or more - -there may be present a smooth, rounded nodule, the size of a pea. This may then break down and form an ulcer with rounded, smooth, and firm pearly gray edges. The ulceration may extend widely, bringing about extreme destruction of all the invaded tissues. It very rarely undergoes cicatrization, and seldom if ever gives metastasis or involves lymph-nodes. The cell nests have a peculiar roset form, due to the short, blunt projections of cells at the periphery. The nuclei are, as a rule, 0, May be likened to a main stem from which arise numerous secondary stems, which in turn give off delicate terminals, consisting entirely of epilong, narrow and spindle shaped, and do not stain deeply. At the periphery of the cell nests the nuclei are arranged somewhat radially.

Fig. 64. - Rodent Ulcer (Mallory).

Fig. 65. - Adenocarcinoma of the Body of the Uterus (Cullen).

It is usually single, but may be multiple and may continue for many years-three to twenty-four.