A Squamous Epithelioma is a carcinoma that has arisen from a surface covered by stratified epithelium such as skin and certain mucous membranes. It occurs most commonly on the cervix, the skin of the face, penis, vagina, and esophagus, especially wherever there is a junction of skin and mucous surfaces.

It makes its appearance as an indurated mass in which ulceration takes place rapidly and exposes a circular surface with raised, hard edges. Sometimes it looks at first like a small wart.

Columns of these cells penetrate the tissues and on account of pressure arrange themselves in successive layers, the inner ones being almost flat and corniried, forming the epithelial pearls. Hyperkeratosis is the term used to indicate the corni-fication.

The presence of these pearls does not indicate that the tumor is necessarily malignant; they mean that the growth was derived from squamous epithelium. They are also not always found in squamous epitheliomata. The growth may have been so rapid as not to have allowed cornincation to take place. As the cells infiltrate the surrounding tissue, there is a well-marked border zone of round cell infiltration, and the elastic tissue, as a rule, shows various forms of degeneration.

The cells are usually quite large, and may show numerous "prickles".

This form of carcinoma differs greatly in its malignancy. Some may exist for several years without showing much tendency to spread, but may suddenly grow and cause extensive destruction of tissue, with subsequent death of the patient. They recur on removal, and give metastasis by the lymphatics.