A sebaceous cyst may reach such dimensions as to simulate a dermoid or thyreo-glossal cyst.
Hydatid and cysticercus cysts have also been met with in the tongue.
Thyreo-glossal Tumours and Cysts.—Tumours may develop in the embryonic tract which passes from the isthmus of the thyreoid gland to the foramen cæcum at the base of the tongue—the thyreo-glossal tract of His. They have the same structure as the thyreoid gland, and occupy the dorsum of the tongue, extending from the foramen cæcum backwards towards the epiglottis, in some cases attaining considerable size. They are of a bluish-brown or dark red colour, and are liable to repeated attacks of hæmorrhage. These tumours sometimes become cystic, the cysts being lined with ciliated epithelium and containing colloid material. Bleeding may take place into a cyst, causing it to become suddenly enlarged, or the cyst may burst and the blood escape into the mouth. These variations in size and repeated attacks of bleeding help to distinguish thyreo-glossal cysts from other swellings of the tongue. Treatment is only called for when the swelling causes interference with speech or swallowing; it consists in removing the tumour by dissection.
When the lower end of the tract becomes cystic it forms a swelling in the neck ([p. 583]).
Malformations.—Complete or partial absence of the tongue is exceedingly rare.
Occasionally the fore part of the tongue is bifid. The function of the organ is not interfered with, and the operation of paring and suturing the two halves is only called for on account of the disfigurement.
Congenital tongue-tie is a condition in which the tip of the tongue is bound down to the floor of the mouth by an abnormally short and narrow frenum, or by folds of mucous membrane on each side of the frenum, so that the tongue cannot be protruded. Although this deformity is rare, it is common for parents to blame an imaginary tongue-tie when a child is slow in learning to speak, or when he speaks indistinctly or stammers, and the doctor is frequently requested to divide the frenum under such circumstances. In the vast majority of cases nothing is found to be wrong with the frenum. In the rare cases of true tongue-tie the edges of the shortened bands should be snipped with scissors close behind the incisor teeth, and then torn with the finger-nail.
Excessive length of the frenum is occasionally met with, and in children may allow of the tongue falling back into the throat and causing sudden suffocative attacks, one of which may prove fatal. In some cases the patient is able voluntarily to fold the tongue back behind the soft palate.
Macroglossia is the term applied to a variety of conditions in which the tongue becomes unduly large, so that it tends to be protruded from the mouth, and to become scored by the teeth. The typical form—lymphangiomatous macroglossia—is due to a dilatation of the lymph spaces of the tongue. It is often congenital, and may affect the whole or only a part of the tongue. The enlargement may be progressive from the first, or may remain stationary for years, and then begin to develop somewhat suddenly, sometimes after an injury or as a result of some infective condition. The treatment consists in removing a wedge-shaped portion of the tongue.
In certain cases of macroglossia in children, the lesion has been found to be a fibromatosis of the nerves of the tongue, analogous to the plexiform neuroma.