[Illustration:  FIG. 47.—­Diffuse Lipomatosis of Neck.]

Lipoma in other Situations.—­The periosteal lipoma is usually congenital, and is most often met with in the hand; it forms a projecting lobulated tumour, which, when situated in the palm, resembles an angioma or a lymphangioma.  The subserous lipoma arises from the extra-peritoneal fat in the posterior abdominal wall, in which case it tends to grow forwards between the layers of the mesentery and to give rise to an abdominal tumour; or it may grow from the extra-peritoneal fat in the anterior abdominal wall and protrude from one of the hernial openings or through an abnormal opening in the parietes, constituting a fatty hernia.  A subsynovial lipoma grows from the fat surrounding the synovial membrane of a joint, and projects into its interior, giving rise to the symptoms of loose body.  Lipomas are also met with growing from the adipose connective tissue between or in the substance of muscles, and, when situated beneath the deep fascia, such as the fascia lata of the thigh, the characteristic signs are obscured and a differential diagnosis is difficult.  It may be differentiated from a cold abscess by puncture with an exploring needle.

[Illustration:  FIG. 48.—­Zanthoma of Hands in a girl aet. 14, showing multiple subcutaneous tumours (cf.  Fig. 49).

(Sir H. J. Stiles’ case.)]

#Zanthoma# is a rare but interesting form of tumour, composed of a fibrous and fatty tissue, containing a granular orange-yellow pigment, resembling that of the corpus luteum.  It originates in the corium and presents two clinical varieties.  In the first of these, it occurs in the form of raised yellow patches, usually in the skin of the eyelids of persons after middle life, and in many instances is associated with chronic jaundice; the patches are often symmetrical, and as they increase in size they tend to fuse with another.

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.

[Illustration:  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