The growths are classified according to the tissues of which they are chiefly composed and from which they originate, and according to their etiology. There are consequently the connective-tissue group; that of tissues of higher function, as muscle, nerve, and vessels; and the epithelial group, in which the new formation of epithelium is the essential feature. The teratoid group comprises a more complex massing of tissues, representing a combination of those derived from all the germinal layers of the embryo. The infective group includes those tumors whose structure is closely allied to that of the products of inflammation, but whose origin is the direct result of the introduction from without of a microphyte.
CONNECTIVE-TISSUE GROUP.
Each member mainly composed of a more or less typical growth of a connective tissue:
Myxoma,
Lipoma,
Glioma,
Chondroma,
Fibroma (including papilloma and melanoma),
Osteoma.
To these are added tumors composed of an atypical growth of a connective tissue, chiefly manifested by a predominance of cells:
Endothelioma,
Sarcoma.
The sarcoma includes as many varieties as there are tissues in this group, hence,
Myxosarcoma,
Liposarcoma,
Gliosarcoma,
Chondrosarcoma,
Fibrosarcoma, melanosarcoma,
Osteosarcoma.
GROUP OF TISSUES OF HIGHER FUNCTION.