Myeloma.—A myeloma is composed of large multinuclear giant cells surrounded by round and spindle cells. The cut surface of the tumour presents a deep red or maroon colour. While occasionally met with in tendon sheaths and bursæ, and is then of an orange-yellow colour, the myeloma occurs most frequently in the cancellous tissue at the ends of the long bones, its favourite site being the upper end of the tibia. Although formerly classified as a sarcoma, it is the exception for it to present malignant features, and it can usually be extirpated by local measures without fear of recurrence. The diagnosis, X-ray appearances, and the method of removal are considered with the diseases of bone. Sometimes the myeloma is met with in multiple form in the skeleton, in association with an unusual form of protein in the urine (Bence Jones).
Myoma.—A myoma is composed of non-striped muscle fibres. A pure myoma is very rare, and is met with in organs possessed of non-striped muscle, such as the stomach, intestine, urinary bladder, and prostate. In the uterus, which is the most common situation, these tumours contain a considerable admixture of fibrous tissue, and are known as fibroids or fibro-myomas. They present on section a fasciculated appearance, which may resemble that of a section of balls of cotton ([Fig. 54]). They are encapsulated and vascular, frequently attain a large size, and may be single or multiple. While they may occasion neither inconvenience nor suffering, they frequently give rise to profuse hæmorrhage from the uterus, and may cause serious symptoms by pressing injuriously on the ureters or the intestine, or by complicating pregnancy and parturition.
The Rhabdomyoma is an extremely rare form of tumour, met with in the kidney, uterus, and testicle. It contains striped muscle fibres, and is supposed to originate from a residue of muscular tissue which has become sequestrated during development.
Fig. 54.—Fibro-myoma of Uterus.
(Anatomical Museum, University of Edinburgh.)
Glioma.—A glioma is a tumour composed of neuroglia. It is met with exclusively in the central nervous system, retina, and optic nerve. It is a slowly growing, soft, ill-defined tumour, which displaces the adjacent nerve centres and nerve tracts, and is liable to become the seat of hæmorrhage and thus to give rise to pressure symptoms resembling apoplexy. The glioma of the retina tends to grow into the vitreous humour and to perforate the globe. It is usually of the nature of a glio-sarcoma and is highly malignant.
Endotheliomas take origin from the endothelium of lymph vessels and blood vessels, and serous cavities. They show great variation in type, partly because of the number of different kinds of endothelium from which they are derived, and partly because the new connective tissue which is formed is liable to undergo transformation into other tissues. They may be soft or hard, solid or cystic, diffuse or circumscribed; they grow very slowly, and are almost always innocent, although recurrence has been occasionally observed. Cases of multiple endotheliomata of the skin have recently been described by Wise.
Angioma, lymphangioma, and neuroma are described with the disease of the individual tissues.