Page:The New International Encyclopædia 1st ed. v. 19.djvu/611

* TUMOK. 531 TUMOB. superficial, developing in the subcutaneous fat. Lipoinata may, however, develop an,vvhere where fat is found and consequently have a wide dis- tribution. They are generally inclosed in firm fibrous capsules and occur usually on the shoul- ders, back, or forearms. Gliondroma. — These are tumors in which the new-formed tissue resembles cartilage of cither the hyalin or fibrous variety. Osteoma. — Osteomata ok bony tumors are rather rare as pure tumors. Associated with other forms of tumor tissue (as osteosarcoma, osteo-fibroma, etc. ), they are more common. Osteomata as a rule develop in bone. Less com- monly they originate in other tissues. Gliuina. — Gliomata are connective-tissue tumors which follow the structure of the nervous system connective tissue, or neuroglia. Gliomata are soft and usually vascular, tlius predisposing to hemorrhage. They are also extremely liable to fatty degeneration. As a pure type they are rare. Associated with other forms of connective- tissue new growths, the glyo-sarcoma, glyo-myxo- ma, etc., they are more common. They occur chiefly in those parts of the nervous system where neuroglia is found, e.g. in the brain and cord, the ganglia, and in the optic and olfactory nerves. Myoma. — ilyomata are tumors hose tissue elements are analogous to those found in muscle tissue. Like normal muscle, they may be divided into two forms, one in which the tissue elements are smooth, or involuntary muscle, the other in which the tissue elements are striated, or vol- untary muscle. To the former the name 'leiomy- oma' or 'myoma levicellulare' has been given, to the latter the name of 'rhabdomyoma' or 'myoma striocellulare.' Myoma is rare. Xeiiroma. — ^Neuromata are divided into true neuromata and the so-called false neuromata. True neuromata are extremely rare. They con- sist of nerve tissue and may be of the ganglionic type in which new nerve cells develop, or of the fibrillar type which consist of new-formed nerve fibres. Neuromata may be single or multiple, the latter frequently occurring along the branches of distribution of a single periplieral nerve. They occur in stumps after amputation of a limb and are often extremely painful. The 'false neuro- niiita' are not neuromata at all, but fibromata, sarcomata, myxomata, etc., of the connective tissue of the nerve trunks. Ancjioma. — These tumors consist of nevl,y formed blood or l.^Tuph vessels and are of two kinds, ha'mangioma and lymphangioma. The former are subdivided into simple angioma or angioma telangiectohles and angioma caverno- sum. The simple angiomata are composed of masses of blood vessels, mainly capillaries, held together by connective tissue. The so-called 'strawberry' marks or vascular mevi, usually of the face, are congenital tumors of this varie- ty- Tumors Sometimes Benign, Sometimes ]Maligna:nt. Eiulothclioma. — These tumors orig- inate from that type of connective tissue known as endothelium which forms the linings of blood vessels, lymphatics, etc. On account of their extremely cellular character and on ac- count of the reduction of their intercellular base- ment substance to a minimum, these tumors bear a close morphological resemblance to the carcinomata, among which they are often classed. Endotheliomata are most common in the pleura, peritoneum, dura mater, and pia mater. Less frequently they occur in brain, liver, ovaries, testicle, lymph nodes, salivary glands, brflie, anil skin. They may be large or small, single or multiple, and may form metastases. Adenoma. — .Adenomata are epithelial tumors in which the epithelium is glandular in type and is arranged in more or less distinct alveoli. They thus correspond in structure to a gland. The alveoli are supported as tumors in the irregu- larity of the arrangement of their component elements. Blocking up of the ducts of the glandular tissue sometimes leads to an accumu- lation of secretion within the alveoli and the formation of cysts. When this cyst formation is a prominent feature of the growth the term cyst-adenoma is used to designate the tumor. Of these the most important is the multilocular cyst-adenoma of the ovary. Most adenomata are non-malignant, rather slow growing tumors. The most connnon sites are the ovary, nianmiary gland, kidney, liver, submaxillary, sulilingual, parotid, thyroid, and lachrymal. They alsn occur in those mucous membranes which are supplied with glands, as for example the mucous mem- branes of the stomach, intestines, nose, pharynx, etc. The most common sites of malignant adeno- mata are the stomach, intestines, manunary gland thyroid, and uterus. JIalignant Tumors. Sarcoma. — Sarcomata are tumors of the connective-tissue group. They dift'er from connective-tissue tumors in that the connective tissue of which the sarcomata are com- posed is of the embryonal form. This has a very distinct bearing upon their malignancy, for, as has been already mentioned, embryonal tissues possess much greater powers of growth than do adult tis.sues. Sarcomata are usually classified according to the character and ar- rangement of their cellular elements. Thus we have small round-celled, large round-celled, small spindle-celled, large spindle-celled, giant- celled or myeloid, stellate-celled sarcoma, etc. The ends of long bones like the tibia and humerus are frequently affected. The mammary glands are sometimes the sites of sarcoma, as also the sheaths of peripheral nerves. Sarcoma is as a rule an affection of early life. From ten to forty it is most common, and uncommon after the latter age. The two sexes are about equally susceptible. Carcinoma. — Carcinomata are malignant tu- mors of epithelial tissue. The epithelium is as varied in character as is normal epithelium. The epithelial elements are supported by a more or less abimdant connective-tissue framework, or stroma, which forms bundles of fibres irregular in arrangement, and in the meshes of which are cavities or alveoli in which the epithelial cells lie loosely without any definite arrangement. In general the epithelial cells conform to the dif- ferent normal types ; but we find, as is the case with all cancerous growths, an irregularity as to shape, size, and arrangement wliieh is much more marked than in normal epithelium. And even in a carcinoma where a particular type of cell predominates, other forms of cell are frequently intermingled with the predom- inating form. Carcinoma occurs as a primary tumor in tis-