myxomatous tissue it is called a
_myxo-adenoma_, and when the gland spaces of the tumour become distended
with accumulated secretion, a _cystic adenoma_, the best examples of
which are met with in the mamma and ovary. A characteristic feature of
the cystic variety is the tendency the tumour tissue exhibits to project
into the interior of the cysts, constituting what are known as
_intracystic growths_. They are essentially innocent, but intracystic
growths, especially in the mamma of women over fifty, should be regarded
with suspicion and therefore should be removed on radical lines.
Transition forms between adenoma and carcinoma are also met with in the
rectum and large intestine, and these should be treated on the same
lines as cancer.

CARCINOMA OR CANCER

A cancer is a malignant tumour which originates in epithelium. The
cancer cells are derived by proliferation from already existing
epithelium, and they invade the sub-epithelial connective tissue in the
form of simple or branching columns. These columns are enclosed in
spaces--termed alveoli--which are probably dilated lymph spaces, and
which communicate freely with the lymph vessels. The cells composing the
columns and filling the alveoli vary with the character of the
epithelium in which the cancer originates. The malignancy of cancer
depends on the tendency which the epithelium has of invading the tissues
in its neighbourhood, and on the capacity of the cells, when
transported elsewhere by the lymph or blood-stream, of giving rise to
secondary growths.

Cancer may arise on any surface covered by epithelium or in any of the
secreting glands of the body, but it is much more common in some
situations than in others. It is frequently met with, for example, in
the skin, in the stomach and large intestine, in the breast, the uterus,
and the external genitals; less frequently in the gall-bladder, larynx,
thyreoid, prostate, and urinary bladder.

Tissues appear to be most liable to cancer when, having attained
maturity, they enter upon the phase of decadence or involution, and this
phase is reached by different tissues at different periods. It is not so
much, therefore, the age of the person in whom it occurs, as the age of
the tissue in which it arises, that determines the maximum incidence of
cancer. Cancer of the stomach appears and attains a maximum frequency
earlier than cancer of the skin; cancer of the uterus and mamma is more
frequent towards the decline