In the second of a series of articles on epithelioma published in 1918, MacCarty and I1 classified such tumors into six types or apparent types and described each. The tumor commonly known as the rodent ulcer has been termed basal-cell epithelioma because its cells tend to differentiate to a form similar to the cells of the basal or germinative layer of the epidermis. This type, which, like other epitheliomas, may be found on any surface covered with protective epithelium, develops practically always above the clavicle. The majority of its lesions attack the cheek, the eyelids, the nose, the forehead, the ear, the canthi and the temporal regions.
Basal-cell epithelioma often appears in the skin as an elevated, whitish nodule which resembles an adenoma or cyst of a sebaceous gland, as an ulcer with indurated borders, or as a scaly lesion. The latter type, which exfoliates its superficial layers to