Mature<unk>  Ovarian<unk>  with hair inside Mature<unk>  of the mediastinum: A horizontal slice of the resected tumor reveals fibrofatty tissue, calcified areas, and a few cystic spaces lined with smooth membrane and containing a hair. In the left lower corner, the involved B5 bronchus is evident. A mature<unk>  is a grade 0<unk> . They are highly variable in form and histology, and may be solid, cystic, or a combination of the two. A mature<unk>  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<unk> s generally are benign, with 0.17-2% of mature cystic<unk> s becoming malignant. Immature<unk>  Immature<unk>  is the malignant counterpart of the mature<unk>  and contains immature tissues which typically show primitive or embryonal neuroectodermal histopathology. Immature<unk>  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<unk> . 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<unk> . Dermoid cyst A dermoid cyst is a mature cystic<unk>  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<unk>  on the skull sutures and in the ovaries of females. Fetus in fetu and fetiform<unk>  Fetus in fetu and fetiform<unk>  are rare forms of mature<unk> s 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<unk>  in having an apparent spine and bilateral symmetry. Most authorities agree that fetiform<unk> s are highly developed mature<unk> s; the natural history of fetus in fetu is controversial. There also may be a cultural difference, with fetiform<unk>  being reported more often in ovarian<unk> s (by gynecologists) and fetus in fetu being reported more often in retroperitoneal<unk> s (by general surgeons). 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 this regard, in many cases the fetus in fetu is reported to occupy a fluid-filled cyst within a mature<unk> . Cysts within mature<unk>  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<unk>  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<unk>  that contains mostly thyroid tissue. Epignathus Epignathus is a rare<unk>  originating in the oropharyngeal area that occurs in utero. It presents with a mass protruding from the mouth at birth. Untreated, breathing is impossible. An EXIT procedure is the recommended initial treatment.
Teratoma
Lipoma
Embryoma
Dermoid cyst
Gonadoblastoma
Spina bifida
Immature teratoma
Blastoma