HISTOID OR CONNECTIVE-TISSUE TUMORS. 81 
What is the structure of a myeloid or giant-celled sarcoma? 
The principal bulk of the tumor is made up of either the round or 
spindle-shaped cells. Mixed with these irregularly are found large 
multi-nucleated cells or giant cells. They occur usually with bone. 
What is an osteo-sarcoma ? 
Tumors are either of the round or spindle-celled variety, in which 
are found irregular masses of newly-formed bone. 
Describe an angio-sarcoma. 
In some sarcomata the bloodvessels form such a prominent feature, 
that is, they are so numerous and their lumina so large, that the tumors 
contain a large amount of blood. The sarcoma cells also are apt to be 
arranged in strings, each having a bloodvessel for its centre. 
What is an alveolar sarcoma ? 
In this form the intercellular substance is arranged as a net, the 
meshes of which resemble alveoli. The sarcoma cells are attached to 
the sides of the alveolus as well as lie free in its cavity. Fine trabecu- 
le from the alveolar walls run between the cells, and by this feature 
we are usually able to differentiate between this form of sarcoma and 
carcinoma. Sometimes, however, this is impossible. 
What are the combinations of sarcoma with other tissue ? 
With myxoma forming myxo-sarcoma. 
With adenoma forming adeno-sarcoma. 
With fat tissue forming lipo-sarcoma. 
With muscle tissue forming myo-sarcoma. 
What is the structure of the endotheliomata ? 
These tumors originate from endothelium by cell proliferation, and 
are often very difficult to differentiate from sarcoma and from carcinoma. 
The individual cells may resemble normal endothelium, or may be 
large, thick and irregular in shape, or may be cuboidal. 
Of what are the lipomata composed ? 
Of fat tissue, and may contain much or little connective tissue. 
They are benign. 
What is the appearance of a section of a chondroma ? 
It resembles cartilage, but the cells are not as uniform in size and 
shape. Small growths on the surfaces of normal cartilages are called 
enchondroses. 
6—H.P.B. 
