The tumour named after the Greek word for monster can grow hair and teeth
A teratoma is a tumour built from several kinds of tissue at once, including hair, muscle, teeth or bone. It starts in the cells that normally become eggs or sperm, or in embryonic cells, and its name joins the Greek word for monster to the usual suffix for tumours.
Teratomas come in two broad types. Mature ones, which include dermoid cysts, are generally benign, though somewhere between 0.17 and 2 percent of mature cystic teratomas turn malignant. Immature teratomas contain primitive, embryo-like tissue and can be cancerous. Most ovarian teratomas are mature, whereas in adults those in the testicle are generally cancerous. Only a tissue biopsy gives a definitive diagnosis, and surgery is the usual treatment, often with chemotherapy for testicular and immature ovarian cases.
They most often appear at the tailbone, in the ovary or in the testicle. At the coccyx they occur in about one in 30,000 newborns, which makes them among the commonest tumours in that age group, and girls are affected more often. Ovarian teratomas account for about a quarter of ovarian tumours and tend to be noticed in middle age, while testicular teratomas make up almost half of testicular cancers. Those from embryonic cells usually sit on the body's midline, from the brain and tongue to the neck and the base of the spine.
Some are genuinely strange. A struma ovarii is made mostly of thyroid tissue. Rare fetiform teratomas and cases of fetus in fetu contain structures resembling a malformed fetus, sometimes with limbs or a torso; fetus in fetu has an apparent spine and symmetry, and has often been read as a twin growing inside its sibling, although its nature remains disputed. Reports of cysts within mature teratomas include partial skull bones and a rudimentary beating heart.
Teratomas can also trigger anti-NMDA receptor encephalitis, an autoimmune illness, because they may harbour immune B cells aimed at NMDA receptors. Immature teratomas are unusual genetically too, with one of the lowest somatic mutation rates of any tumour type. Since ultrasound became routine, some are spotted before birth, particularly at the tailbone or neck, where they protrude into the amniotic fluid.
Source: Teratoma
