In the neck, axilla, and pubes a diffuse overgrowth of the subcutaneous fat is sometimes met with, forming symmetrical tumour-like masses, known as _diffuse lipoma_. As this is not, strictly speaking, a tumour, the term _diffuse lipomatosis_ is to be preferred. A similar condition was described by Jonathan Hutchinson as being met with in the domestic animals. If causing disfigurement, the mass of fat may be removed by operation. [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 æt. 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.]