The Epithelioma of the skin forms the majority of the flat-celled epitheliomas, and it has been already considered.

The two most interesting forms are the ordinary flat-celled epithe lioma and the rodent ulcer. The former is met with most frequently in the lower lip, but also occurs not uncommonly in the penis and scrotum. In the last mentioned seat it appears to occur with special frequency in chimney-sweepers and in workers in paraffin-refineries. The rodent ulcer occurs in the face, especially on the eyelids and side of nose.

The flat-celled epithelioma not infrequently occurs in scars or in old ulcers. In the latter case it may penetrate into the sinuses, and even reach cavities in bones.

Ordinary cancer is of rare occurrence in the skin, but cases have been observed to which the names scirrhus and soft cancer have been given. It may develop in a lupus. Pigmented cancers are of occasional occurrence, and they are of importance on account of their tendency to form secondary tumours, first in the lymphatic glands and then throughout the body. They are, however, much less frequent than melanotic sarcomas, with which they are apt to be confused.

Literature

Ichthyosis - Jahn, Ichthyosis congenita, 1869; Kyber, Wien. med. Jahrb., 1880; Hilton Fagge, Guy's Hosp. Hep., xv., 1869; Esoff, Virch. Arch., lxix., 1877. Keloid - Alibert, Malad. de la peau, 1814; Virchow, Oeschwiilste, ii.; Neelsen, Langenbeck's Arch., xxiv.; Lanohans, Virch. Arch., xl., 1866. MolluHcum contagiosum - Virchow, Virch. Arch., xxxiii., I860; Thin, Jour, of Anat. and Phys., xvi., 1881. Myoma - Judassohn, Virch. Arch., exxi., 1890. Xeroderma pigmentosum - KAPOSI, Wien. med. Jahrb., 1882; Taylor, Med. Record. 1888; M'Call Anderson, Dis. of skin, 1894. Seaman's skin - Unna, in Orth's Lehrb., 1894.