They are commonly met with in
adults, on the scalp (Fig. 99), face, neck, back, and external genitals.
Sometimes they are multiple, and they may be met with in several members
of the same family. They are smooth, rounded, or discoid cysts, varying
in size from a split-pea to a Tangerine orange. In consistence they are
firm and elastic, or fluctuating, and are incorporated with the
overlying skin, but movable on the deeper structures. The orifice of the
partly blocked sebaceous follicle is sometimes visible, and the contents
of the cyst can be squeezed through the opening. The wall of the cyst is
composed of a connective-tissue capsule lined by stratified squamous
epithelium. The contents consist of accumulated epithelial cells, and
are at first dry and pearly white in appearance, but as a result of
fatty degeneration they break down into a greyish-yellow pultaceous and
semi-fluid material having a peculiar stale odour. It is probable that
the decomposition of the contents is the result of the presence of
bacteria, and that from the surgical point of view they should be
regarded as infective. A sebaceous cyst may remain indefinitely without
change, or may slowly increase in size, the skin over it becoming
stretched and closely adherent to the cyst wall as a result of friction
and pressure. The contents may ooze from the orifice of the duct and dry
on the skin surface, leading to the formation of a sebaceous horn
(Fig. 100). As a result of injury the cyst may undergo sudden
enlargement from haemorrhage into its interior.

Recurrent attacks of inflammation frequently occur, especially in wens
of the face and scalp. Suppuration may ensue and be followed by cure of
the cyst, or an offensive fungating ulcer forms which may be mistaken
for epithelioma. True cancerous transformation is rare.

Wens are to be _diagnosed_ from dermoids, from fatty tumours, and from
cold abscesses. Dermoids usually appear before adult life, and as they
nearly always lie beneath the fascia, the skin is movable over them. A
fatty tumour is movable, and is often lobulated. The confusion with a
cold abscess is most likely to occur in wens of the neck or back, and it
may be impossible without the use of an exploring needle to
differentiate between them.

[Illustration: FIG. 99.--Multiple Sebaceous Cysts or Wens; the larger
ones are of many years' duration.]

_Treatment._--The removal of wens is to be recommended while they are
small and freely mova