TUMORS 165 



EPITHELIOMA 



This is a type of cancer. A case was broiij^ht to the hibora- 

 tory with the liistory tliat it had a "j>-rowth" on the side of 

 the head for several months. The tumor was tiat and about 

 one inch in diameter. A microscopic exaniiuation rcvcah-d it 

 to be an epithelioma. 



OSTEOMA 



Osteoma is a term applied to a tumor that consists of case- 

 ous tissue. This kind of tumor usually arises from the bones 

 of the skeleton but may develop in parts away from the nor- 

 mal bony structure. 



Osteomata usually occur singly in the body, that is, they 

 are localized. If the new bony growth arises in connection 

 with the skeleton it may be designated according to its loca- 

 tions and relations. 



If the new bony growth is small and circumscribed and 

 attached to the old bone it is called an osteophyte. If it be 

 larger and more tumor-like it is called an exostosis. If the 

 newly circumscribed bony growth is located within the bone 

 cavity it is called an enostosis. 



New bony growths not attached to the skeleton may be 

 classified as follows : those which have their seat in the peri- 

 osteum but are separated from the bone are called movable 

 periosteal exostoses; those lying near the bone are called 

 periosteal osteomata; those located some distance from the 

 bone, in muscle and tendon and disconnected, osteomata ; and 

 those situated in other organs, as the lungs, mucous mem- 

 brane of the trachea, the skin or abdominal walls, are hetero- 

 plastic. 



Osteomata may occur either single or multiple. Frequently 

 there are found multiple, circumscribed bony growths in great 

 numbers on the bones of the extremities and trunk. The 

 favorite seat of these new bony growths appears to be on the 

 epiphyseal ends of the bones and the point of insertion of 

 tendons, or both may be involved in the same individual and 

 at the same time. Zeigler says it is probable that such growths 

 are to be referred to as inherited predisposition of the part 

 affected to overgrowth, or to a disturbance in the development 

 of the skeleton. The bony plates and spicules, which in rare 

 cases develop in the lungs or in the mucous membrane oV the 

 air passages, may occur in large numbers. 



The development of the bone takes place partly through 

 the formation of osteoblasts, and partly through metaplasia 

 of formed tissues. The matrix is formed chiefly from the 



