Document 26rZDaXVQq23EREDe1XnrjJ5

TUMORS OF THE SKIN 285 originating from the proliferation of the adjacent glandular epithelium. It may be mentioned that a similar mechanism is apparently active in the forma tion of the epidermal cysts seen after the subcutaneous injection of scarlet oil into the ears of rabbits. The probability of a genesis of epithelial cysts from the surface epithelium, on the other hand, is suggested by the processes leading to the epithelization of osteomyelitic sinuses, of the cavity of the middle ear following perforations of the ear drum (leading sometimes to the formation of cholesteatomas) (Kelemen), of traumatic dentigerous cysts of the jaw (Blum; Morehead and Dewey), and by the development of epi thelial cysts in the iris of the eye, following perforating injuries to the eyeball (Bonnet and Paufique; Moore). X. MALIGNANT POTENTIALITY Accidentally or experimentally produced epithelial cysts of the epidermis represent excellent evidence contradicting the dogma of Ribbert that traumatically misplaced epidermis may form a predisposed anlage for carcinogenesis. It is a well established fact that these traumatic epithelial lesions exhibit almost no cancerigenic tendencies (Teutschlaender), in spite of the statement of Ewing that many become malignant. There is only a single case on record for which a secondary cancerization is claimed (Franke). A cornified squamous cell carcinoma was found in this particular epithelial cyst occupying about one half of its circumference. Attempts which were made to bring about a malignant transformation of the epithelial lining of experimentally produced cysts by causing an additional irritation through the intracystic injection of normal saline, olive oil, distilled water, 10 per cent sodium chloride solution, scarlet red and tar, made 2 to 3 times weekly, succeeded only in stimulating a transitory growth of the cyst with the production of peculiar cystic, endotheliomatoid formations in the surrounding tissue, while the epithelial lining remained without any appre ciable proliferative activity (Burckhardt). The refractory behaviour of traumatic epithelial cysts toward a secondary cancerization is in strong contrast to the malignant tendencies displayed by sebaceous gland cysts which have their favorite localization in the skin of the scalp, face, back and scrotum (Seff and Berkowitz; Caylor). In a series of 236 sebaceous gland cysts observed by Caylor, 12 were cancerous (3.44 per cent). The majority showed squamous cell carcinomas, a few were of the basal cell type. Bishop studied 119 sebaceous gland cysts and keratomas (firm, solid tumors with a lamellated structure arising from the epithelial lining of the sebaceous ducts) and found 11 carcinomatous and 2 precancerous lesions (9.2 per cent). Stone reported an incidence of 2.2 per cent of malignant transformations in his series of sebaceous cysts. A total of 87 cases of card- ^ nomas originating in sebaceous gland cysts was collected from the literature by Collins. It is remarkable in this connection that keratomas seem to be devoid