Fibroma.—Pure fibromata are rare and chiefly seen in the sheaths of nerves (fig. 1o) where they are often multiple, the larynx, the gums forming one variety of so-called epulis and the subcutaneous tissue (painful sub cutaneous nodule). But almost all tumours contain some admix ture of fibrous tissue and of these the commonest and most important are the so-called fibroids of the uterus (see under Myoma).
Myoma.—This tumour is composed of muscle fibres, unstriated except in one very rare variety rhabdo-myo-sarcoma. Pure myo mata are rare and sometimes found in the oesophagus, stomach and bladder. In the uterus, with more or less admixture of fibrous tissue, and therefore better termed fibro-myomata, they are very common. They originate in the wall of the uterus, but generally come to project either internally into the cavity of the uterus, or externally into the peritoneal cavity; and often their sole con nection with the uterine wall is a stalk or pedicle formed from the capsule of the tumour. Fibromyomata of the uterus occur in married and unmarried women and are most common from 35 to 45 years of age; in girls under 20 they are almost unknown. They may attain a great size and are often multiple. Not every fibroid 'Figs. 5, 6, 7, 8, 13, 14 and 16 have been redrawn from Bland Sut ton's Tumours, by permission; figs. 9, 50, II and 12 are from Rose & Carless, Surgery, by permission.
is a source of danger or discomfort, for in many cases they are discovered by chance or not until after death. On the other hand they may give rise to severe symptoms, in many different ways (see GYNAECOLOGY). A fibroid tends to prevent conception, whilst, should pregnancy occur miscarriage is common, and if carried to term, labour is greatly impeded. Occasionally a fibroid undergoes sarcomatous change.
Osteoma (fig. 7).—Bony tu mours not infrequently arise from the bones of the head or face.
They grow very slowly, and are so hard that surgical removal may be very difficult. They also occur as irregular outgrowths from the bones of the limbs, and are then known as Exostoses (fig.
8). A common site for these is the inner and lower end of the femur, at the point of attach ment of the adductor muscle, and such a tumour seems to originate from an ossification of the ten don of this muscle.
Chondroma (fig. 9).—Cartil aginous tumours occur chiefly in children and young people, growing from the bones of the limbs in the neighbourhood of the joints. They are frequently multiple, especially in the hands and feet, but never affect the terminal phalanges. These tumours grow slowly and are quite painless.
Odontoma.—Several varieties of this tumour have been de scribed arising in connection with the teeth and due to delayed or faulty development. They may cause great deformity of the jaw.
Myxoma.—This is composed of loose, gelatinous connective tissue similar to that found in the umbilical cord. Some nasal polypi seem to be of this nature, but true myxomatous tumours are rare. It is, however, not un common for a fibroma or a sar coma to be converted by degener ation into myxomatous-like tissue.
Neuroma.—A pure neuroma is very uncommon, but a tumour known as a Pseudo-neuroma is to be often found in the course of a nerve. This is formed by a localized overgrowth of the fibrous tissue of the nerve sheath.
Glioma.—This variety of tumour arises from the neuroglia, the supporting tissue of the brain and spinal cord. Consequently gliomata are only found in these two struc tures, and the retina which is really an extension of the brain.
Angioma.—This consists of a mesh-work of blood vessels bound together by a small amount of fat and fibrous tissue. Two va rieties are described : (a) The simple nae vus, or port-wine stain, scarcely deserves to be called a tumour. It appears as a reddish blue discolouration of the skin due to over growth and dilatation of the underlying blood-vessels. This condition is most com monly found in the face or scalp, and may be of congenital origin. (b) In the cavern ous naevus the vascular hypertrophy is on a larger scale, and may produce a definite pulsating tumour. Here, again the head is the usual situation. (For illustrations see PATHOLOGY.) Sarcoma.—This is the malignant type of the connective-tissue tumour. Hence, fibro-sarcoma, chondro-sarcoma, osteo-sarcoma, glio-sarcoma, etc., are met with. The general arrangement of a sar coma shows a mass of atypical cells loosely bound together by a small amount of connective tissue. The cells vary greatly in size and shape in dif ferent tumours, and in accordance with the prevailing type the following varieties of sarcoma have been described: (i.) round cell sarcoma, (ii.) spindle-cell sarcoma, (iii.) melanotic sarcoma, (iv.) myeloid sar coma. Nevertheless the melanotic growth is held by many authorities not to be of connective tissue origin and therefore a sar coma, but epithelial and therefore a carcin oma. To it the non-committal name melanoma is often given. Similarly the myeloid variety owing to its peculiar char acters is by many excluded from the group of sarcomata and placed in a separate class "myeloma." The round and spindle cell varieties contain the great majority of all sarcomata, and may occur in almost any part of the body, but they are especially liable to attack the bones (fig.
1). A sarcoma of bone may be either periosteal when it grows from the perios teum covering the outer surface of the bone, or endosteal when it lies in the med ullary cavity. A peculiar form of sar coma, by many classified as an endo thelioma, is found in the parotid and other salivary glands. The cells are usually spin dle-shaped, and among them lie scattered masses of cartilage and fibrous tissue. These tumours are seldom very malignant, and dissemination is rare (fig. 12). The mela noma consists of cells widely irregular in shape and may be pale yellow or brown or black owing to the presence of few or many granules of pigment (melanin) in and among the tumour cells. A melanotic sar coma may arise from a pigmented wart or mole, or from the pigmented layers of the retina. The primary growth is usually small, but dissemination occurs with great rapidity throughout the body.
Melanomata are intensely malig nant, whether the cells contain little or much melanin. The myeloid sarcoma, or myeloma (fig. 13), is composed of irregu larly shaped cells amongst which are large multinucleated cells like the myeloplaxes of bone marrow (see BONES, ANATOMY