A teratoma is a tumor made up of several different types of tissue, such as hair, muscle, teeth, or bone. Teratomata typically form in the tailbone (where it is known as a sacrococcygeal teratoma), ovary, or testicle.
Symptoms
Symptoms may be minimal if the tumor is small. A testicular teratoma may present as a painless lump. Complications may include ovarian torsion, testicular torsion, or hydrops fetalis.
They are a type of germ cell tumor (a tumor that begins in the cells that give rise to sperm or eggs). They are divided into two types: mature and immature. Mature teratomas include dermoid cysts and are generally benign. Immature teratomas may be cancerous. Most ovarian teratomas are mature. In adults, testicular teratomas are generally cancerous. Definitive diagnosis is based on a tissue biopsy.
Treatment of coccyx, testicular, and ovarian teratomas is generally by surgery. Testicular and immature ovarian teratomas are also frequently treated with chemotherapy.
Teratomas occur in the coccyx in about one in 30,000 newborns, making them one of the most common tumors in this age group. Females are affected more often than males. Ovarian teratomas represent about a quarter of ovarian tumors and are typically noticed during middle age. Testicular teratomas represent almost half of testicular cancers. They can occur in both children and adults. The term comes from the Greek word for "monster" plus the "-oma" suffix used for tumors.
Types
Mature teratoma
A mature teratoma is a grade 0 teratoma. They are highly variable in form and histology, and may be solid, cystic, or a combination of the two. A mature teratoma often contains several different types of tissue such as skin, muscle, and bone. Skin may surround a cyst and grow abundant hair (see dermoid cyst). Mature teratomas generally are benign, with 0.17-2% of mature cystic teratomas becoming malignant.
Immature teratoma
Immature teratoma is the malignant counterpart of the mature teratoma and contains immature tissues which typically show primitive or embryonal neuroectodermal histopathology. Immature teratoma has one of the lowest rates of somatic mutation of any tumor type and results from one of five mechanisms of meiotic failure.
Gliomatosis peritoneii
Gliomatosis peritoneii, which presents as a deposition of mature glial cells in the peritoneum, is almost exclusively seen in conjunction with cases of ovarian teratoma. Through genetic studies of exome sequence, it was found that gliomatosis is genetically identical to the parent ovarian tumor and developed from cells that disseminate from the ovarian teratoma.
Dermoid cyst
A dermoid cyst is a mature cystic teratoma containing hair (sometimes very abundant) and other structures characteristic of normal skin and other tissues derived from the ectoderm. The term is most often applied to teratoma on the skull sutures and in the ovaries of females.
Fetus in fetu and fetiform teratoma
Fetus in fetu and fetiform teratoma are rare forms of mature teratomas that include one or more components resembling a malformed fetus. Both forms may contain or appear to contain complete organ systems, even major body parts, such as a torso or limbs. Fetus in fetu differs from fetiform teratoma in having an apparent spine and bilateral symmetry.
Most authorities agree that fetiform teratomas are highly developed mature teratomas; the natural history of fetus in fetu is controversial. It has been noted that fetiform teratoma is reported more often (by gynecologists) in ovarian teratomas, and fetus in fetu is reported more often (by general surgeons) in retroperitoneal teratomas. Fetus in fetu has often been interpreted as a fetus growing within its twin. As such, this interpretation assumes a special complication of twinning, one of several grouped under the term parasitic twin. In many cases, the fetus in fetu is reported to occupy a fluid-filled cyst within a mature teratoma. Cysts within mature teratomas may have partially-developed organ systems: reports include cases of partial cranial bones, long bones and a rudimentary, beating heart.
Regardless of whether fetus in fetu and fetiform teratoma are one entity or two, they are distinct from and not to be confused with ectopic pregnancy.
Struma ovarii
A struma ovarii (also known as goitre of the ovary or ovarian goiter) is a rare form of mature teratoma that contains mostly thyroid tissue.