Myxoma is a tumor in which mucoid elements or a gelatinoid degeneration
and infiltration containing mucin is a prominent feature. The _mucous
tissue_ which constitutes the tumor may differ little from ordinary
connective tissue except that the intercellular spaces contain mucin.
Histologically the tissue consists of cells embedded in a homogeneous
matrix. The cells may be of various forms, round, (in recent formations)
and spindle-shaped or star-shaped, but especially the latter, in the
older. When incised a fluid containing mucus escapes in greater or less
abundance. While this has properties resembling albumen it is
distinguished by the fact that the precipitate thrown down in it by
alcohol is softened and redissolved on the addition of water. The
precipitate thrown down in an albuminous liquid is insoluble in water.
The formation of this mucous exudate is liable to be followed by fat so
that Virchow considered it as antecedent to fat formation. This is
especially noticeable in the early stages of the cholesteatomata of the
choroid plexus of the horse, in which, as observed by Fürstenberg,
Lassaigne, and Verheyen, the new formation is at first a myxoma, which
later becomes filled up with cholesterine.
Recent observations tend to discredit the alleged distinctive character
of myxoma. The meshes of all connective tissue contain a perceptible
amount of mucin. Œdematous subcutaneous connective tissue contains this
mucin in greater proportion and approximates to the condition of mucous
tissue. The umbilical cord, which has been long advanced as the
physiological type of mucous tissue, has been shown to consist of
ordinary connective tissue with an abundance of fluid in its meshes.
Koster denies that the myxoma is a special type of tumor, and holds that
it is only a condition that may arise in any tumor which contains
connective tissue. In other words, myxoma is only an œdematous condition
of the connective tissue neoplasm—fibroma, sarcoma, carcinoma, etc.—due
to passive congestion or other circulatory disturbance.
As seen in the brain of the horse the formation is usually of the nature
of a myxo-lipoma, as the final outcome is usually the cholesterine
bearing mass. In other cases the connective tissue spaces become further
distended with the viscous, gelatinoid liquid and form veritable
cysts—myxoma-cystoides.
In tumors of this kind affecting the choroid plexus the chain of
symptoms is essentially the same as given under cholesteatoma and the
prognosis is nearly equally grave. It need only be said that in recent
cases in which there is as yet little permanent tissue, measures may
sometimes be hopefully adopted, to secure the reabsorption of liquid
constituents, and even perchance to remove some obvious cause of passive
congestion upon which the effusion depends.