The second form occurs in children and adolescents; it may affect several generations of the same family, and is often multiple, there being a combination of thickened yellow patches of skin and projecting tumours, some of which may attain a considerable size ([Figs. 48] and [49]). On section, the tumour tissue presents a brilliant orange or saffron colour.
There is no indication for removing the tumours unless for the deformity which they cause; exposure to the X-rays is to be preferred to operation.
Fig. 49.—Zanthoma showing Subcutaneous Tumours on Buttocks. From same patient as [Fig. 48].
Chondroma.—A chondroma is mainly composed of cartilage. Processes of vascular connective tissue pass in between the nodules of cartilage composing the tumour from the fibrous capsule which surrounds it. On section it is of a greyish-blue colour and semi-translucent. The tumour is firm and elastic in consistence, but certain portions may be densely hard from calcification or ossification, while other portions may be soft and fluctuating as a result of myxomatous degeneration and liquefaction. These tumours grow slowly and painlessly, and may surround nerves and arteries without injuring them. They may cause a deep hollow in the bone from which they originate. All intermediate forms between the innocent chondroma and the malignant chondro-sarcoma are met with. Chondroma may occur in a multiple form, especially in relation to the phalanges and metacarpal bones. When growing in the interior of a bone it causes a spindle-shaped enlargement of the shaft, which in the case of a phalanx or metacarpal bone may resemble the dactylitis resulting from tubercle or syphilis. A chondroma appears as a clear area in a skiagram.
Fig. 50.—Chondroma growing from infraspinous fossa of Scapula.
A skiagram of a bone in which there is a chondroma shows a clear rounded area in the position of the tumour, which must be differentiated from similar clear areas due to other kinds of tumour, especially the myeloma; when it has undergone calcification or ossification, it gives a shadow as dark as bone.