Malignant transformation
A "benign" grade 0 (mature) teratoma nonetheless has a risk of malignancy. Recurrence with malignant endodermal sinus tumor has been reported in cases of formerly benign mature teratoma, even in fetiform teratoma and fetus in fetu. Squamous cell carcinoma has been found in a mature cystic teratoma at the time of initial surgery. A grade 1 immature teratoma that appears to be benign (e.g., because AFP is not elevated) has a much higher risk of malignancy, and requires adequate follow-up. This grade of teratoma also may be difficult to diagnose correctly. It can be confused with other small round cell neoplasms such as neuroblastoma, small cell carcinoma of hypercalcemic type, primitive neuroectodermal tumor, Wilms tumor, desmoplastic small round cell tumor, and non-Hodgkin lymphoma.A teratoma with malignant transformation  is a very rare form of teratoma that may contain elements of somatic malignant tumors such as leukemia, carcinoma, or sarcoma. Of 641 children with pure teratoma, nine developed TMT: five carcinoma, two glioma, and two embryonal carcinoma (here, these last are classified among germ cell tumors). Extraspinal ependymoma
Extraspinal ependymoma, usually considered to be a glioma (a type of nongerm cell tumor), may be an unusual form of mature teratoma. Treatment
Surgery
The treatment of choice is complete surgical removal (i.e., complete resection). Teratomas are normally well-encapsulated and noninvasive of surrounding tissues, hence they are relatively easy to resect from surrounding tissues. Exceptions include teratomas in the brain, and very large, complex teratomas that have pushed into and become interlaced with adjacent muscles and other structures.
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 ovary, testicle, or coccyx. 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.